> ## Documentation Index
> Fetch the complete documentation index at: https://docs.codeant.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Plsql

> [accordion] Jump statements should not be redundant
>
> Jump statements, such as `RETURN and CONTINUE` let you change the default flow of program execution, but jump statements that direct the control flow to the original direction are just a waste of keystrokes.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE PROCEDURE print_numbers AS
> BEGIN
> FOR i in 1..4 LOOP
> DBMS_OUTPUT.PUT_LINE(i);
> CONTINUE; -- Noncompliant
> END LOOP;
> RETURN;     -- Noncompliant
> END;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> CREATE PROCEDURE print_numbers AS
> BEGIN
> FOR i in 1..4 LOOP
> DBMS_OUTPUT.PUT_LINE(i);
> END LOOP;
> END;
> ```

> [accordion] Predefined exceptions should not be overridden
>
> Naming custom exceptions the same as predefined ones, while technically acceptable, is not a good practice.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> no_data_found EXCEPTION; -- Noncompliant, overrides an Oracle predefined exception
>
> d VARCHAR2(1);
> BEGIN
> SELECT dummy INTO d FROM DUAL WHERE dummy = 'Y'; -- Will raise STANDARD.NO_DATA_FOUND
> EXCEPTION
> WHEN NO_DATA_FOUND THEN
> DBMS_OUTPUT.PUT_LINE('No data found!'); -- Won't be executed, as NO_DATA_FOUND was overriden, confusing!
> WHEN OTHERS THEN
> DBMS_OUTPUT.PUT_LINE('Unknown error!'); -- *Will* be executed
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> my_own_exception EXCEPTION; -- Compliant
>
> d VARCHAR2(1);
> BEGIN
> SELECT dummy INTO d FROM DUAL WHERE dummy = 'Y'; 
> EXCEPTION
> WHEN NO_DATA_FOUND THEN
> DBMS_OUTPUT.PUT_LINE('No data found!'); -- *Will* be executed
> WHEN OTHERS THEN
> DBMS_OUTPUT.PUT_LINE('Unknown error!');
> END;
> /
> ```

> [accordion] Lines in a multiline comment should start with \*
>
> Multi-line comments are more readable when each line is aligned using the "\*" character. At most one violation is created for each comment
>
> ```plsql Bad theme={"theme":"css-variables"}
> /*
> this line is not aligned and ugly Non-Compliant
> no violation is created on this line, even though is it also bad
> */
>
> /* this is Compliant */
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> /*
> * this is much better Compliant
> */
>
> /* this is Compliant */
> ```

> [accordion] FETCH ... BULK COLLECT INTO should be used
>
> The `FETCH ... INTO statement is inefficient when used in a loop (where many records are expected). It leads to many context-switches between the SQL and PL/SQL engines. Instead, the FETCH ... BULK COLLECT INTO` statement will issue the SQL requests in bulk, minimizing context switches.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> CREATE TABLE largeTable AS SELECT ROWNUM AS id FROM all_objects;
>
> SET TIMING ON
> DECLARE
> x PLS_INTEGER;
> CURSOR largeCursor IS SELECT ROWNUM FROM largeTable;
> largeTableRowId BINARY_INTEGER;
> BEGIN
> OPEN largeCursor;
>
> x := 0;
> LOOP
> FETCH largeCursor INTO largeTableRowId; -- Noncompliant
> EXIT WHEN largeCursor%NOTFOUND;
>
> x := x + largeTableRowId;
> END LOOP;
>
> DBMS_OUTPUT.PUT_LINE('Sum of rownums using alternative 1: ' || x);
>
> CLOSE largeCursor;
> END;
> /
> SET TIMING OFF
>
> DECLARE
> r largeTable%ROWTYPE;
> CURSOR myCursor IS SELECT * FROM largeTable;
> BEGIN
> OPEN myCursor;
> FETCH myCursor INTO r; -- Compliant, outside of a loop
> CLOSE myCursor;
> END;
> /
>
> DROP TABLE largeTable;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> CREATE TABLE largeTable AS SELECT ROWNUM AS id FROM all_objects;
>
> SET TIMING ON
> DECLARE
> x PLS_INTEGER;
> CURSOR largeCursor IS SELECT * FROM largeTable;
> TYPE largeTableRowIdArrayType IS TABLE OF BINARY_INTEGER INDEX BY BINARY_INTEGER;
> largeTableRowIdArray largeTableRowIdArrayType;
> BEGIN
> OPEN largeCursor;
>
> x := 0;
> LOOP
> FETCH largeCursor BULK COLLECT INTO largeTableRowIdArray LIMIT 1000; -- Compliant
>
> FOR i IN largeTableRowIdArray.FIRST .. largeTableRowIdArray.LAST LOOP
>   x := x + largeTableRowIdArray(i);
> END LOOP;
>
> EXIT WHEN largeCursor%NOTFOUND;
> END LOOP;
>
> DBMS_OUTPUT.PUT_LINE('Sum of rownums using alternative 2: ' || x);
>
> CLOSE largeCursor;
> END;
> /
> SET TIMING OFF
>
> DECLARE
> r largeTable%ROWTYPE;
> CURSOR myCursor IS SELECT * FROM largeTable;
> BEGIN
> OPEN myCursor;
> FETCH myCursor INTO r; -- Compliant, outside of a loop
> CLOSE myCursor;
> END;
> /
>
> DROP TABLE largeTable;
> ```

> [accordion] CASE should be used rather than DECODE
>
> `DECODE is an old function that has been replaced by the easier to understand and more common CASE. Unlike DECODE, CASE` may also be used directly within PL/SQL.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> operand CHAR(1) := 'B';
> l_result PLS_INTEGER;
> BEGIN
> -- Noncompliant
> SELECT DECODE(operand, 'A', 1
>                    , 'B', 2
>                    , 'C', 3
>                    , 'D', 4
>                    , 'E', 5
>                    , 'F', 6
>                    , 7)
> INTO l_result
> FROM dual;
>
> DBMS_OUTPUT.PUT_LINE('l_result = ' || l_result); -- 2
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> operand CHAR(1) := 'B';
> l_result PLS_INTEGER;
> BEGIN
>
> l_result := CASE operand
>             WHEN 'A' THEN 1
>             WHEN 'B' THEN 2
>             WHEN 'C' THEN 3
>             WHEN 'D' THEN 4
>             WHEN 'E' THEN 5
>             WHEN 'F' THEN 6
>             ELSE 7
>           END;
>
> DBMS_OUTPUT.PUT_LINE('l_result = ' || l_result); -- 2
> END;
> /
> ```

> [accordion] Column aliases should be defined using AS
>
> For better readability, column aliases should be used with the `AS` keyword. If it is missing, it could be misread as another column being selected.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> result DUAL.dummy%TYPE;
> BEGIN
> SELECT
> dummy d -- Non-Compliant - could be misread as selecting both "dummy" and a column "d"
> INTO
> result
> FROM
> DUAL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> result DUAL.dummy%TYPE;
> BEGIN
> SELECT
> dummy AS d -- Compliant
> INTO
> result
> FROM
> DUAL;
> END;
> /
> ```

> [accordion] Procedures and functions should be encapsulated in packages
>
> Having a bunch of standalone functions or procedures reduces maintainability because it becomes harder to find them and to see how they are related. Instead, they should be logically grouped into meaningful packages.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE PROCEDURE show_name(name VARCHAR2) AS -- Non-Compliant
> BEGIN
> DBMS_OUTPUT.PUT_LINE('Name: ' || name);
> END;
> /
>
> DROP PROCEDURE show_name;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> CREATE PACKAGE employee AS
> PROCEDURE show_name;
> END;
> /
>
> CREATE PACKAGE BODY employee AS
> name VARCHAR2(42);
>
> PROCEDURE show_name AS  -- Compliant
> BEGIN
> DBMS_OUTPUT.PUT_LINE('Name: ' || name);
> END;
> END;
> /
>
> DROP PACKAGE employee;
> ```

> [accordion] FUNCTIONS should not have OUT parameters
>
> Functions with `OUT parameters are complex to understand. Indeed, it is impossible to tell, just by looking at the function call, whether an argument is a input or output. Moreover, functions with OUT` parameters cannot be called from SQL. It is better to either break such functions up into smaller ones, which each return a single value, or to return several values at once, by combining them in a collection, record, type, or table row.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> CREATE TABLE employee(
> firstName VARCHAR2(42),
> name VARCHAR2(42),
> phone VARCHAR2(42)
> );
>
> INSERT INTO employee VALUES ('John', 'Smith', '+1');
>
> DECLARE
> firstName VARCHAR2(42);
> name VARCHAR2(42);
> phone VARCHAR2(42);
>
> -- This DOES NOT return the employee name
> FUNCTION getEmployeeInfos(firstName OUT VARCHAR2, phone OUT VARCHAR2) RETURN VARCHAR2 AS -- Non-Compliant, confusing
> name VARCHAR2(42);
> BEGIN
> SELECT firstName, name, phone INTO firstName, name, phone FROM employee;
> RETURN name;
> END;
> BEGIN
> name := getEmployeeInfos(firstName, phone);
>
> DBMS_OUTPUT.PUT_LINE('firstName: ' || firstName);
> DBMS_OUTPUT.PUT_LINE('name: ' || name);
> DBMS_OUTPUT.PUT_LINE('phone: ' || phone);
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> CREATE TABLE employee(
> firstName VARCHAR2(42),
> name VARCHAR2(42),
> phone VARCHAR2(42)
> );
>
> INSERT INTO employee VALUES ('John', 'Smith', '+1');
>
> DECLARE
> emp employee%ROWTYPE;
>
> FUNCTION getEmployeeInfos RETURN employee%ROWTYPE AS -- Compliant
> emp employee%ROWTYPE;
> BEGIN
> SELECT * INTO emp FROM employee;
> RETURN emp;
> END;
> BEGIN
> emp := getEmployeeInfos;
>
> DBMS_OUTPUT.PUT_LINE('firstName: ' || emp.firstName);
> DBMS_OUTPUT.PUT_LINE('name: ' || emp.name);
> DBMS_OUTPUT.PUT_LINE('phone: ' || emp.phone);
> END;
> /
>
> DROP TABLE employee;
> ```

> [accordion] Nested loops should be labeled
>
> Labeled loops are useful, especially when the code is badly indented, to match the begin and end of each loop. When loops are nested, labeling them can improve the code’s readability. This rule detects nested loops which do not have a start label.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> LOOP
> LOOP -- Noncompliant, this nested loop is not labeled
>   EXIT;
> END LOOP;
>
> EXIT;
> END LOOP;
>
> FOR i IN 1..10  LOOP
> WHILE true LOOP -- Noncompliant, this nested loop has no start label
>   EXIT;
> END LOOP nestedLoopLabel1;
>
> EXIT;
> END LOOP;
>
> WHILE true LOOP
> <<nestedLoopLabel2>>
> LOOP -- Compliant, but better with an end label
>   EXIT;
> END LOOP;
>
> EXIT;
> END LOOP;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> BEGIN
> LOOP
> <<nestedLoopLabel0>>
> LOOP
>   EXIT;
> END LOOP nestedLoopLabel0;
>
> EXIT;
> END LOOP;
>
> FOR i IN 1..10  LOOP
> <<nestedLoopLabel1>>
> WHILE true LOOP
>   EXIT;
> END LOOP nestedLoopLabel1;
>
> EXIT;
> END LOOP;
>
> WHILE true LOOP
> <<nestedLoopLabel2>>
> LOOP
>   EXIT;
> END LOOP nestedLoopLabel2;
>
> EXIT;
> END LOOP;
> END;
> /
> ```

> [accordion] FORMS\_DDL(COMMIT) and FORMS\_DDL(ROLLBACK) should not be used
>
> `FORMS_DDL` command, like every DDL statements, is performing an implicit COMMIT. It should be used only if there is no pending transaction otherwise this transaction is automatically committed without updating the Form statuses. Also, the potentially acquired locks are lost in case of this implicit COMMIT.
>
> "FORMS\_DDL('COMMIT')" and "FORMS\_DDL('ROLLBACK')" should be used with care and most of the time, "COMMIT\_FORM" or "ROLLBACK\_FORM" should be preferred.
>
> Check the Oracle Forms documentation for more details.
>
> ```plsql Bad theme={"theme":"css-variables"}
> FORMS_DDL('COMMIT');
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> COMMIT_FORM;
> ```

> [accordion] Block start and end labels should match
>
> Labeled blocks are useful, especially when the code is badly indented, to match the begin and end of each block. This rule verifies that block start and end labels match, when both are specified.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> NULL;
> END; -- Compliant, no labels at all
> /
>
> <<myBlockLabel1>>
> BEGIN
> NULL;
> END; -- Compliant, only starting label
> /
>
> BEGIN
> NULL;
> END myBlockLabel2; -- Compliant, only ending label
> /
>
> <<myBlockLabel3>>
> BEGIN
> NULL;
> END myBlockLabel4; -- Noncompliant, labels mismatch
> /
>
> <<myBlockLabel6>>
> <<myBlockLabel6>>
> BEGIN
> NULL;
> END myBlockLabel6; -- Noncompliant, several starting labels
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> BEGIN
> NULL;
> END;
> /
>
> <<myBlockLabel1>>
> BEGIN
> NULL;
> END;
> /
>
> BEGIN
> NULL;
> END myBlockLabel2;
> /
>
> <<myBlockLabel3>>
> BEGIN
> NULL;
> END myBlockLabel3;
> /
>
> <<myBlockLabel6>>
> BEGIN
> NULL;
> END myBlockLabel6;
> /
> ```

> [accordion] Individual WHERE clause conditions should not be unconditionally true or false
>
> `WHERE clause conditions that reinforce or contradict the definitions of their columns are useless; they are always either unconditionally true or unconditionally false. For instance, there’s no point in including AND column IS NOT NULL` if the column is defined as non-null.
>
> **Noteworthy**
>
> This rule raises issues only when a **Data Dictionary** is provided during the analysis. See \[[https://docs.sonarqube.org/latest/analysis/languages/plsql/](https://docs.sonarqube.org/latest/analysis/languages/plsql/)]\([https://docs.sonarqube.org/latest/analysis/languages/plsql/](https://docs.sonarqube.org/latest/analysis/languages/plsql/))
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE TABLE product
> (id INT,
> name VARCHAR(6) NOT NULL,
> mfg_name VARCHAR(6),
> mfg_id INT
> ...
>
> SELECT name, price
> FROM product
> WHERE name is not null -- Noncompliant; always true. This column is NOT NULL
> AND mfg_name = 'Too long name' -- Noncompliant; always false. This column can contain only 6 characters
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] NATURAL JOIN queries should not be used
>
> `NATURAL JOIN` is a type of equi-join which implicitly compares all identically-named columns of the two tables. While this a feature which may seem convenient at first, it becomes hard to maintain over time.
>
> Consider an EMPLOYEE table with the columns FULL\_NAME, and DEPT\_ID, and a DEPARTMENT table with the columns DEPT\_ID, and NAME. A natural join between those tables will join on the DEPT\_ID column, which is the only identically-named column.
>
> But, if a new NAME column is later added to the EMPLOYEE table, then the join will be done on both DEPT\_ID and NAME. Natural joins make simple changes such as adding a column complicated and are therefore better avoided.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> SELECT *
> INTO employeeArray
> FROM employee
> NATURAL JOIN departement; -- Non-Compliant, the join predicate is implicit
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> BEGIN
> SELECT *
> INTO employeeArray
> FROM employee
> JOIN departement
> USING (dept_id);  -- Compliant, explicit join predicate
> END;
> /
> ```

> [accordion] Object attributes should comply with a naming convention
>
> Shared coding conventions allow teams to collaborate efficiently. This rule checks that object attribute names match the provided regular expression.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE TYPE my_type AS OBJECT(
> foo__bar INTEGER             -- Non-Compliant
> );
> /
>
> DROP TYPE my_type;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> CREATE TYPE my_type AS OBJECT(
> foo_bar INTEGER              -- Compliant
> );
> /
>
> DROP TYPE my_type;
> ```

> [accordion] Procedures should not contain RETURN statements
>
> Procedures, unlike functions, do not return values. The `RETURN statement therefore, when used within a procedure, is used to prematurely end the procedure. However, having multiple exit points (i.e. more than the END` of the procedure itself), increases the complexity of the procedure and makes it harder to understand and debug.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> PROCEDURE prcoedureWithReturn AS
> BEGIN
> RETURN; -- Noncompliant
>
> DBMS_OUTPUT.PUT_LINE('prcoedureWithReturn called'); -- This is actually unreachable
> END;
> BEGIN
> prcoedureWithReturn;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] CASE should be used for sequences of simple tests
>
> When a single primitive is tested against three or more values in an `IF, ELSIF chain, it should be converted to a CASE` instead for greater readability.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> x PLS_INTEGER := 0;
> BEGIN
> IF x = 0 THEN                     -- Noncompliant
> DBMS_OUTPUT.PUT_LINE('x = 0');
> ELSIF x = 1 THEN
> DBMS_OUTPUT.PUT_LINE('x = 1');
> ELSE
> DBMS_OUTPUT.PUT_LINE('x > 1');
> END IF;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> x PLS_INTEGER := 0;
> BEGIN
> CASE x
> WHEN 0 THEN
>   DBMS_OUTPUT.PUT_LINE('x = 0');
> WHEN 1 THEN
>   DBMS_OUTPUT.PUT_LINE('x = 1');
> ELSE
>   DBMS_OUTPUT.PUT_LINE('x > 1');
> END CASE;
> END;
> /
> ```

> [accordion] TO\_NUMBER should be used with a format model
>
> The \`TO\_NUMBER function is converting the value of BINARY\_FLOAT, BINARY\_DOUBLE, CHAR, VARCHAR2, NCHAR, or NVARCHAR2 datatype to a value of NUMBER datatype.
>
> Without providing the format of the input, TO\_NUMBER will consider the provided value is compliant with the default format. Relying on a default configuration is a source of error because it creates a dependency between the code and the configuration of the ORACLE server where this code is deployed.
>
> The behaviour of the TO\_NUMBER\` function will certainly not be the expected one if the configuration of the ORACLE server is changing.
>
> ```plsql Bad theme={"theme":"css-variables"}
> IF ( TO_NUMBER(p_string) >= 0 and TO_NUMBER(p_string) <= TO_NUMBER('50.00') ) THEN
> RETURN 1;
> ELSE
> RETURN 0;
> END IF;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> IF ( TO_NUMBER(p_string, '99.99') >= 0 and TO_NUMBER(p_string, '99.99') <= TO_NUMBER('50.00','99.99') ) THEN
> RETURN 1;
> ELSE
> RETURN 0;
> END IF;
> ```

> [accordion] Types should follow a naming convention
>
> Shared coding conventions allow teams to collaborate efficiently. This rule checks that type names match the provided regular expression.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> TYPE Collection_type_ IS VARRAY(42) OF PLS_INTEGER; -- Noncompliant
> BEGIN
> NULL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> TYPE collectionType IS VARRAY(42) OF PLS_INTEGER;
> BEGIN
> NULL;
> END;
> /
> ```

> [accordion] The RELIES\_ON clause should not be used
>
> Since Oracle 11.2, `RELIES_ON` has been deprecated because the dependencies of result cache-enabled functions are automatically computed.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE OR REPLACE FUNCTION foo RETURN PLS_INTEGER RESULT_CACHE RELIES_ON(DUAL) AS -- Noncompliant
> BEGIN
> RETURN 0;
> END;
> /
>
> DROP FUNCTION foo;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> CREATE OR REPLACE FUNCTION foo RETURN PLS_INTEGER RESULT_CACHE AS
> BEGIN
> RETURN 0;
> END;
> /
>
> DROP FUNCTION foo;
> ```

> [accordion] COALESCE should be preferred to NVL
>
> `NVL was introduced by Oracle Database during the 80’s. COALESCE is a more modern function part of ANSI-92 standard than can replace NVL. Use of COALESCE should be preferred to NVL` for performance reason if the two parameters provided have the same type. COALESCE is running faster than NVL thanks to its short-circuit evaluation of the parameters.
>
> In order to avoid "ORA-00932: inconsistent datatypes" error, double-check the two arguments of the NVL function have the same type before switching to COALESCE.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SELECT employee_uuid, NVL(TO_CHAR(bonus_pct), 'not this year') "Bonus" FROM employees
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SELECT employee_uuid, COALESCE(TO_CHAR(bonus_pct), 'not this year') "Bonus" FROM employees
> ```

> [accordion] EXECUTE IMMEDIATE should be used instead of DBMS\_SQL procedure calls
>
> `EXECUTE IMMEDIATE` is easier to use and understand than the DBMS\_SQL package’s procedures. It should therefore be preferred, when possible.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> CREATE TABLE myTable(
> foo VARCHAR2(42)
> );
>
> CREATE PROCEDURE drop_table(tableName VARCHAR2) AS
> cursorIdentifier INTEGER;
> BEGIN
> cursorIdentifier := DBMS_SQL.OPEN_CURSOR; -- Compliant; this is not a procedure call
> DBMS_SQL.PARSE(cursorIdentifier, 'DROP TABLE ' || tableName, DBMS_SQL.NATIVE); -- Noncompliant
> DBMS_SQL.CLOSE_CURSOR(cursorIdentifier); -- Noncompliant
>
> DBMS_OUTPUT.PUT_LINE('Table ' || tableName || ' dropped.');
> EXCEPTION
> WHEN OTHERS THEN
> DBMS_SQL.CLOSE_CURSOR(cursorIdentifier); -- Noncompliant
> END;
> /
>
> BEGIN
> drop_table('myTable');
> END;
> /
>
> DROP PROCEDURE drop_table;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> CREATE TABLE myTable(
> foo VARCHAR2(42)
> );
>
> CREATE PROCEDURE drop_table(tableName VARCHAR2) AS
> cursorIdentifier INTEGER;
> BEGIN
> EXECUTE IMMEDIATE 'DROP TABLE ' || tableName;
> DBMS_OUTPUT.PUT_LINE('Table ' || tableName || ' dropped.');
> END;
> /
>
> BEGIN
> drop_table('myTable');
> END;
> /
>
> DROP PROCEDURE drop_table;
> ```

> [accordion] DML events clauses should not include multiple OF clauses
>
> The DML events clause of a trigger is not meant to be used with multiple \`OF conditions. When it is, only the last one will actually be taken into account, without any error message being produced. This can lead to counter-intuitive code.
>
> Only the UPDATE event should have an OF\` condition, and there should be at most one occurence of it.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE OR REPLACE TRIGGER myTrigger
> BEFORE UPDATE OF firstName OR UPDATE OF lastName -- Noncompliant - will *only* be triggered on updates of lastName!
> ON myTable
> FOR EACH ROW
> BEGIN
> NULL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> CREATE OR REPLACE TRIGGER myTrigger
> BEFORE UPDATE OF firstName, lastName             -- Compliant - triggered on updates of firstName or/and lastName
> ON myTable
> FOR EACH ROW
> BEGIN
> NULL;
> END;
> /
> ```

> [accordion] EXIT should not be used in loops
>
> FOR and WHILE loops are structured control flow statements.
>
> A FOR loop will iterate once for each element in the range, and the WHILE iterates for as long as a condition holds.
>
> However, inserting an `EXIT` statement within the loop breaks this structure, reducing the code’s readability and making it harder to debug.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> TYPE myCollectionType IS VARRAY(10) OF VARCHAR2(42);
> myCollection myCollectionType := myCollectionType('Foo', 'Bar', NULL, 'Baz', 'Qux');
>
> i PLS_INTEGER;
> BEGIN
> i := 1;
> WHILE i <= myCollection.LAST LOOP
> EXIT WHEN myCollection(i) IS NULL; -- Noncompliant, breaks the structure of the WHILE
>
> DBMS_OUTPUT.PUT_LINE('Got: ' || myCollection(i));
> i := i + 1;
> END LOOP;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> TYPE myCollectionType IS VARRAY(10) OF VARCHAR2(42);
> myCollection myCollectionType := myCollectionType('Foo', 'Bar', NULL, 'Baz', 'Qux');
>
> i PLS_INTEGER;
> BEGIN
> i := 1;
> WHILE i <= myCollection.LAST AND myCollection(i) IS NOT NULL LOOP
> DBMS_OUTPUT.PUT_LINE('Got: ' || myCollection(i));
> i := i + 1;
> END LOOP;
> END;
> /
> ```

> [accordion] %TYPE and %ROWTYPE should be used
>
> The use of `%TYPE and %ROWTYPE` is an easy way to make sure that a variable’s type always matches the type of the relevant column in an existing table. If the column type changes, then the variable changes with it.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE FUNCTION func1(acc_no IN NUMBER) 
> RETURN NUMBER 
> IS total NUMBER(11,2); -- Noncompliant
> BEGIN 
>   SELECT order_total 
>   INTO total -- total is assigned here: it could be defined as orders.order_total%TYPE
>   FROM orders 
>   WHERE customer_id = acc_no; 
>   RETURN(total); 
> END;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> CREATE FUNCTION func1(acc_no IN NUMBER) 
> RETURN NUMBER 
> IS total orders.order_total%TYPE;
> BEGIN 
>   SELECT order_total 
>   INTO total
>   FROM orders 
>   WHERE customer_id = acc_no; 
>   RETURN(total); 
> END;
> ```

> [accordion] Loops with at most one iteration should be refactored
>
> A loop with at most one iteration is equivalent to the use of an \`IF statement to conditionally execute one piece of code. No developer expects to find such usage of a loop statement. If the initial intention of the author was really to conditionally execute one piece of code, an IF statement should be used in place.
>
> At worst that was not the initial intention of the author and so the body of the loop should be fixed to use the nested RETURN, EXIT, RAISE or GOTO\` statements in a more appropriate way.
>
> ```plsql Bad theme={"theme":"css-variables"}
> LOOP
> counter := counter + 1;
> dbms_output.put_line(counter);
> EXIT;   -- Noncompliant
> END LOOP;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> LOOP
> counter := counter + 1;
> IF counter > 10 THEN
> EXIT;
> ELSE 
> dbms_output.put_line(counter);
> END IF;
> END LOOP;
> ```

> [accordion] TO\_DATE and TO\_TIMESTAMP should be used with a datetime format model
>
> The \`TO\_DATE and TO\_TIMESTAMP functions are converting char of CHAR, VARCHAR2, NCHAR, or NVARCHAR2 datatype to respectively a value of DATE or TIMESTAMP datatype.
>
> Without providing the format of the input char, TO\_DATE will consider the provided char is compliant with the default date format. Relying on a default configuration is a source of error because it creates a dependency between the code and the configuration of the ORACLE server where this code is deployed.
>
> According to the Oracle’s documentation "the default date format is determined implicitly by the NLS\_TERRITORY initialization parameter or can be set explicitly by the NLS\_DATE\_FORMAT parameter.". It means the behaviour of the TO\_DATE\` function will certainly not be the expected one if the configuration of the ORACLE server is changing.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SELECT TO_DATE( 'January 15, 2018, 11:00 A.M.')
> FROM DUAL;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SELECT TO_DATE( 'January 15, 2018, 11:00 A.M.', 'Month dd, YYYY, HH:MI A.M.')
> FROM DUAL;
> ```

> [accordion] Queries should not SELECT too many columns
>
> \`SELECT queries that return too many columns may be complex or difficult to maintain.
>
> This rule identifies queries that SELECT\` more than the specified number of columns.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> SELECT id, name, firstname, gender, height, weight, age -- Noncompliant
> INTO peopleArray
> FROM people
> WHERE age > 60;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] DBMS\_OUTPUT.PUT\_LINE should not be used
>
> The output of `DBMS_OUTPUT.PUT_LINE is not always visible, for example when SERVEROUTPUT is set to OFF`. Moreover, there is no standardized way to specify the importance of the message. It is better to use a logging mechanism instead.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> BEGIN
> DBMS_OUTPUT.PUT_LINE('An error occured'); -- Noncompliant
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] Constant declarations should contain initialization assignments
>
> Constants must be immediately initialized at declaration. They cannot be reassigned any value after the declaration, as they are constant. This rule prevents PLS-00322 exceptions from being raised at runtime.
>
> The following code snippet illustrates this rule:
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> foo CONSTANT PLS_INTEGER NULL; -- Noncompliant PLS-00322
> bar CONSTANT PLS_INTEGER NOT NULL; -- Noncompliant PLS-00322
> aa CONSTANT PLS_INTEGER; -- Noncompliant
> BEGIN
> NULL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> foo CONSTANT PLS_INTEGER NULL :=42;
> bar CONSTANT PLS_INTEGER NOT NULL := 42;
> aa CONSTANT PLS_INTEGER := 42; -- Compliant
> BEGIN
> NULL;
> END;
> /
> ```

> [accordion] cursor%NOTFOUND should be used instead of NOT cursor%FOUND
>
> `cursor%NOTFOUND is clearer and more readable than NOT cursor%FOUND`, and is preferred.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> CURSOR c IS SELECT DUMMY FROM DUAL;
> x VARCHAR2(1);
> BEGIN
> OPEN c;
> FETCH c INTO x;
> IF NOT c%FOUND THEN  -- Noncompliant
> DBMS_OUTPUT.PUT_LINE('uh?');
> ELSE
> DBMS_OUTPUT.PUT_LINE('all good: ' || x);
> END IF;
> CLOSE c;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> CURSOR c IS SELECT DUMMY FROM DUAL;
> x VARCHAR2(1);
> BEGIN
> OPEN c;
> FETCH c INTO x;
> IF c%NOTFOUND THEN 
> DBMS_OUTPUT.PUT_LINE('uh?');
> ELSE
> DBMS_OUTPUT.PUT_LINE('all good: ' || x);
> END IF;
> CLOSE c;
> END;
> /
> ```

> [accordion] Constraints should not be applied to types that cannot be constrained
>
> Some types cannot be constrained, and attempting to do so results in the exception `PLS-00566: type name "..." cannot be constrained` being raised.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> foo BLOB(42); -- Noncompliant - raises PLS-00566: type name "BLOB" cannot be constrained
> BEGIN
> NULL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> foo BLOB;
> BEGIN
> NULL;
> END;
> /
> ```

> [accordion] Procedures and functions should be documented
>
> Each function and procedure should be documented with a comment either just before or right after the `IS or AS` keyword it to explain its goal and how it works.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE FUNCTION my_function RETURN PLS_INTEGER AS
> BEGIN
> RETURN 42;
> END;
> /
>
> CREATE PACKAGE my_package AS
>
> PROCEDURE my_procedure;
>
> FUNCTION my_function RETURN PLS_INTEGER;
>
> END my_package;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> CREATE FUNCTION my_function RETURN PLS_INTEGER AS
> -- Computes the meaning of life
> BEGIN
> RETURN 42;
> END;
> /
>
> CREATE PACKAGE my_package AS
>
> -- This is documentation
> PROCEDURE my_procedure;
>
> /*
> This is documentation
> */
> FUNCTION my_function RETURN PLS_INTEGER;
>
> END my_package;
> /
> ```

> [accordion] Size should be specified for string variables
>
> String data types, such as `VARCHAR2 or NVARCHAR2 require a size constraint. Omitting the size results in the exception PLS-00215: String length constraints must be in range (1 .. 32767)` being raised.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> foo VARCHAR2; -- Noncompliant - raises PLS-00215
> BEGIN
> NULL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> foo VARCHAR2(42); -- Compliant
> BEGIN
> NULL;
> END;
> /
> ```

> [accordion] Complex IF statements should be replaced by CASE statements
>
> Complex chains of IF, ELSIF and ELSE statements should be replaced by the more readable CASE one. A complex IF statement has either several ELSIF clauses, or both an ELSIF and an ELSE clause.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> x PLS_INTEGER := 0;
> BEGIN
> IF x = 0 THEN                     -- Noncompliant
> DBMS_OUTPUT.PUT_LINE('x = 0');
> ELSIF x = 1 THEN
> DBMS_OUTPUT.PUT_LINE('x = 1');
> ELSIF x = 2 THEN
> DBMS_OUTPUT.PUT_LINE('x = 2');
> END IF;
> END;
> /
>
> DECLARE
> x PLS_INTEGER := 0;
> y PLS_INTEGER := 0;
> BEGIN
> IF x = 0 THEN                     -- Noncompliant
> DBMS_OUTPUT.PUT_LINE('x = 0, y = ?');
> ELSIF y = 1 THEN
> DBMS_OUTPUT.PUT_LINE('x != 0, y = 1');
> ELSE
> DBMS_OUTPUT.PUT_LINE('x != 0, y != 1');
> END IF;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> x PLS_INTEGER := 0;
> BEGIN
> CASE x
> WHEN 0 THEN
>   DBMS_OUTPUT.PUT_LINE('x = 0');
> WHEN 1 THEN
>   DBMS_OUTPUT.PUT_LINE('x = 1');
> WHEN 2 THEN
>   DBMS_OUTPUT.PUT_LINE('x = 2');
> ELSE
>   -- Do not forget the ELSE to prevent ORA-06592
>   NULL;
> END CASE;
> END;
> /
>
> DECLARE
> x PLS_INTEGER := 0;
> y PLS_INTEGER := 0;
> BEGIN
> CASE                              -- Compliant
> WHEN x = 0 THEN
>   DBMS_OUTPUT.PUT_LINE('x = 0, y = ?');
> WHEN y = 1 THEN
>   DBMS_OUTPUT.PUT_LINE('x != 0, y = 1');
> ELSE
>   DBMS_OUTPUT.PUT_LINE('x != 0, y != 1');
> END CASE;
> END;
> /
> ```

> [accordion] Record fields should comply with a naming convention
>
> Shared coding conventions allow teams to collaborate efficiently. This rule checks that all record field names match the provided regular rexpression.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> TYPE my_type IS RECORD(
> foo__bar PLS_INTEGER   -- Non-Compliant
> );
> BEGIN
> NULL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> TYPE my_type IS RECORD(
> foo_bar PLS_INTEGER    -- Compliant
> );
> BEGIN
> NULL;
> END;
> /
> ```

> [accordion] Oracles join operator (+) should not be used
>
> Developers should use the `FROM ... OUTER JOIN syntax rather than the Oracle join operator (). The reason is that outer join queries that use  are subject to several restrictions which do not apply to the FROM ... OUTER JOIN syntax. For instance, a WHERE condition containing the + operator cannot be combined with another condition using the OR` logical operator.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> -- Noncompliant
> SELECT *
> INTO employeesArray
> FROM employee, department
> WHERE employee.DepartmentID = department.ID(+);
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> BEGIN
> -- Compliant
> SELECT *
> INTO employeesArray
> FROM employee LEFT OUTER JOIN department
> ON employee.DepartmentID = department.ID;
> END;
> /
> ```

> [accordion] WHEN OTHERS should not be the only exception handler
>
> Before trapping all possible exceptions, it is best to try to trap the specific ones and try to recover from those.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> CREATE TABLE hitCounter
> (
> page VARCHAR2(42),
> hits NUMBER,
> CONSTRAINT pk PRIMARY KEY (page)
> );
>
> CREATE PROCEDURE hitPage(pageIn VARCHAR2) AS
> BEGIN
> INSERT INTO hitCounter VALUES (pageIn, 1);
> EXCEPTION -- Noncompliant, the only exception handler is WHEN OTHERS
> WHEN OTHERS THEN
> IF SQLCODE = -1 THEN
>   UPDATE hitCounter SET hits = hits + 1 WHERE page = pageIn;
> ELSE
>   DBMS_OUTPUT.PUT_LINE('An unknown error occured!');
> END IF;
> END;
> /
>
> BEGIN
> hitPage('index.html');
> hitPage('index.html');
> END;
> /
>
> SELECT * FROM hitCounter;
>
> DROP PROCEDURE hitPage;
> DROP TABLE hitCounter;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> CREATE TABLE hitCounter
> (
> page VARCHAR2(42),
> hits NUMBER,
> CONSTRAINT pk PRIMARY KEY (page)
> );
>
> CREATE PROCEDURE hitPage(pageIn VARCHAR2) AS
> BEGIN
> INSERT INTO hitCounter VALUES (pageIn, 1);
> EXCEPTION
> WHEN DUP_VAL_ON_INDEX THEN
> UPDATE hitCounter SET hits = hits + 1 WHERE page = pageIn;
> WHEN OTHERS THEN
> DBMS_OUTPUT.PUT_LINE('An unknown error occured!');
> END;
> /
>
> BEGIN
> hitPage('index.html');
> hitPage('index.html');
> END;
> /
>
> SELECT * FROM hitCounter;
>
> DROP PROCEDURE hitPage;
> DROP TABLE hitCounter;
> ```

> [accordion] FULL OUTER JOINS should be used with caution
>
> Full outer joins aren’t in common use, and as a result many developers don’t really understand them. Therefore, each use of this language feature should be reviewed.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> SELECT *
> BULK COLLECT INTO result
> FROM DUAL d1
> FULL OUTER JOIN DUAL d2 ON d1.dummy != d2.dummy; -- Noncompliant
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] SYNCHRONIZE should not be used
>
> `SYNCHRONIZE was introduced by Oracle as a recovery mechanism in case there is a loss of synchronization between what is in memory and what is displayed. It works but it comes with a price; each call to SYNCHRONIZE` generates a network round-trip between the server and the Forms client. Most of the time it should be avoided or used with caution as explicitly stated in the Oracle Forms documentation.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SYNCHRONIZE;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] Procedures should have parameters
>
> Procedures which don’t accept parameters are likely to either not be reused that often or to depend on global variables instead. Refactoring those procedures to take parameters will make them both more flexible and reusable.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> name VARCHAR2(42) := 'John';
>
> PROCEDURE print_name; -- Noncompliant
>
> PROCEDURE print_name AS -- Noncompliant
> BEGIN
> DBMS_OUTPUT.PUT_LINE('Name: ' || name);
> END;
>
> BEGIN
> print_name;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> PROCEDURE print_name(name VARCHAR2) AS -- Compliant
> BEGIN
> DBMS_OUTPUT.PUT_LINE('Name: ' || name);
> END;
> BEGIN
> print_name('John');
> END;
> /
> ```

> [accordion] END LOOP should be followed by a semicolon
>
> Labeled loops are useful, especially when the code is badly indented, to match the begin and end of each loop. However, those labels, if used, must appear on the same line as the "END" keyword in order to avoid any confusion. Indeed, the label might otherwise be seen as a procedure call.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> PROCEDURE foo AS
> BEGIN
> DBMS_OUTPUT.PUT_LINE('foo was called!');
> END;
> BEGIN
> LOOP
> EXIT;
> END LOOP -- The semicolon was forgotten
>
> foo; -- Noncompliant, This is interpreted as a label of the previous FOR loop, not as a procedure call to foo!
>
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> PROCEDURE foo AS
> BEGIN
> DBMS_OUTPUT.PUT_LINE('foo was called!');
> END;
> BEGIN
>
> <<myLoopLabel>>
> LOOP
> EXIT;
> END LOOP myLoopLabel;
>
> foo; -- Correctly interpreted as a procedure call to foo
> END;
> /
> ```

> [accordion] Inserts should include values for non-null columns
>
> Any insert which omits a value for a `NOT NULL` column in a database table will be automatically rejected by the database unless a default value has been specified for the column.
>
> **Noteworthy**
>
> This rule raises issues only when a **Data Dictionary** is provided during the analysis. See \[[https://docs.sonarqube.org/latest/analysis/languages/plsql/](https://docs.sonarqube.org/latest/analysis/languages/plsql/)]\([https://docs.sonarqube.org/latest/analysis/languages/plsql/](https://docs.sonarqube.org/latest/analysis/languages/plsql/))
>
> ```plsql Bad theme={"theme":"css-variables"}
> INSERT INTO MY_TABLE  -- Noncompliant; N2 value omitted
> (
> N1
> )
> VALUES
> (
> 1
> )
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> INSERT INTO MY_TABLE  -- Compliant even though N3 value not supplied
> (
> N1,
> N2
> )
> VALUES
> (
> 1,
> 'Paul'
> )
> ```

> [accordion] WHEN OTHERS clauses should be used for exception handling
>
> Ensure that every possible exception is caught by using a `WHEN OTHERS` clause.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> result PLS_INTEGER;
> custom_exception EXCEPTION;
> BEGIN
> result := 42 / 0;                            -- "Unexpected" division by 0
>
> RAISE custom_exception;
> EXCEPTION                                      -- Non-Compliant
> WHEN custom_exception THEN
> DBMS_OUTPUT.PUT_LINE ('custom_exception: ' || DBMS_UTILITY.FORMAT_ERROR_STACK);
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> result PLS_INTEGER;
> custom_exception EXCEPTION;
> BEGIN
> result := 42 / 0;                            -- "Unexpected" division by 0
>
> RAISE custom_exception;
> EXCEPTION                                      -- Compliant
> WHEN custom_exception THEN
> DBMS_OUTPUT.PUT_LINE ('custom_exception: ' || DBMS_UTILITY.FORMAT_ERROR_STACK);
> WHEN OTHERS THEN
> DBMS_OUTPUT.PUT_LINE ('other: ' || DBMS_UTILITY.FORMAT_ERROR_STACK);
> END;
> /
> ```

> [accordion] UNION ALL should be preferred to UNION
>
> \`UNION is significantly less performant compared to UNION ALL because it removes duplicated entries and run an internal DISTINCT to achieve this.
>
> UNION ALL is not removing duplicates and returns all the results from the queries. It performs faster in most of the cases compared to UNION. Nevertheless, the quantity of data returned by UNION ALL can be significantly more important than with UNION. On slow network, the performance gain to use UNION ALL instead of UNION can be challenged by the time lost to transfer more data than with UNION\`.
>
> ```plsql Bad theme={"theme":"css-variables"}
> -- if you care about not having duplicated entries, then UNION is the good choice
> SELECT EMAIL FROM EMPLOYEES UNION SELECT EMAIL FROM CUSTOMERS
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> -- if you don't care about duplicated entries in the results of this UNION, then UNION ALL should be preferred
> SELECT EMAIL FROM EMPLOYEES UNION ALL SELECT EMAIL FROM CUSTOMERS
> ```

> [accordion] END statements of labeled blocks should be labeled
>
> Labeled blocks are useful, especially when the code is badly indented, to match the begin and end of each block. This check detects labeled blocks which are missing an ending label.
>
> ```plsql Bad theme={"theme":"css-variables"}
> <<myBlockLabel1>>
> BEGIN
> NULL;
> END; -- Noncompliant; this labeled loop has no ending label
> /
>
> BEGIN
> NULL; -- Compliant; not a labeled block
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> <<myBlockLabel2>>
> BEGIN
> NULL;
> END myBlockLabel2;
> /
>
> BEGIN
> NULL;
> END;
> /
> ```

> [accordion] Parameter IN mode should be specified explicitly
>
> By default, the parameter mode is `IN`. However, specifying it explicitly makes the code easier to read.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> PROCEDURE printName(name VARCHAR2) AS -- Noncompliant; relies on default mode
> BEGIN
> DBMS_OUTPUT.PUT_LINE('name: ' || name);
> END;
>
> BEGIN
> printName('Foo');
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> PROCEDURE printName(name IN VARCHAR2) AS
> BEGIN
> DBMS_OUTPUT.PUT_LINE('name: ' || name);
> END;
> BEGIN
> printName('Foo');
> END;
> /
> ```

> [accordion] GOTO should not be used within loops
>
> The use of `GOTO in general is arguable. However, when used within loops, GOTO` statements are even more evil, and they can often be replaced by other constructs.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> i PLS_INTEGER := 0;
> BEGIN
> LOOP
> IF i = 3 THEN
>   GOTO loopEnd; -- Noncompliant
> END IF;
>
> DBMS_OUTPUT.PUT_LINE('i = ' || i);
>
> i := i + 1;
> END LOOP;
>
> <<loopEnd>>
> DBMS_OUTPUT.PUT_LINE('Loop end');
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> i PLS_INTEGER := 0;
> BEGIN
> LOOP
> EXIT WHEN i = 3; -- Compliant
>
> DBMS_OUTPUT.PUT_LINE('i = ' || i);
>
> i := i + 1;
> END LOOP;
>
> DBMS_OUTPUT.PUT_LINE('Loop end');
> END;
> /
> ```

> [accordion] Identical expressions should not be used on both sides of a binary operator
>
> Using the same value on either side of a binary operator is almost always a mistake. In the case of logical operators, it is either a copy/paste error and therefore a bug, or it is simply wasted code, and should be simplified.
>
> This rule ignores operators `+, * and ||, and expressions: 1=1, 1<>1, 1!=1, 1~=1 and 1^=1`.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SELECT code
> FROM Person
> WHERE first_name IS NULL OR first_name IS NULL; -- Noncompliant
>
> SELECT * FROM Users
> INNER JOIN Clients ON Clients.id = Clients.id; -- Noncompliant
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SELECT code
> FROM Person
> WHERE first_name IS NULL OR last_name IS NULL;
>
> SELECT * FROM Users
> INNER JOIN Clients ON Clients.id = Users.id;
> ```

> [accordion] Comments should not be nested
>
> PL/SQL does not support nested C-style (`/* ... */`) comments.
>
> ```plsql Bad theme={"theme":"css-variables"}
> /*
> This is a comment block, for which the ending tag was omitted
> It may be difficult to figure out that the following line of code is actually commented
>
>
> variable = function_call();
> /* variable contains the result, this is not allowed, as it is an attempt to create an inner comment */
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] Deprecated LONG and LONG RAW datatypes should no longer be used
>
> The `LONG and LONG RAW datatypes are deprecated and Oracle recommends to migrate them to the LOB datatypes CLOB, NCLOB or BLOB`.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE TABLE images(
> data LONG RAW
> );
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> CREATE TABLE images(
> data BLOB
> );
> ```

> [accordion] Related IF/ELSIF statements and WHEN clauses in a CASE should not have the same condition
>
> A `CASE and a chain of IF/ELSIF statements is evaluated from top to bottom. At most, only one branch will be executed: the first one with a condition that evaluates to true`.
>
> Therefore, duplicating a condition automatically leads to dead code. Usually, this is due to a copy/paste error. At best, it’s simply dead code and at worst, it’s a bug that is likely to induce further bugs as the code is maintained, and obviously it could lead to unexpected behavior.
>
> ```plsql Bad theme={"theme":"css-variables"}
> IF param == 1 THEN
> x := 'A';
> ELSIF param == 2 THEN
> x := 'B';
> ELSIF param == 1 THEN -- Noncompliant, for sure this is a bug
> x := 'C';
> END IF;
>
> result := CASE param
> WHEN 1 THEN 'A'
> WHEN 2 THEN 'B'
> WHEN 1 THEN 'C'  -- Noncompliant
> ELSE 'D'
> END;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> IF param == 1 THEN
> result := 'A';
> ELSIF param == 2 THEN
> result := 'B';
> ELSIF param == 3 THEN
> result := 'C';
> END IF;
>
> result := CASE param
> WHEN 1 THEN 'A'
> WHEN 2 THEN 'B'
> WHEN 3 THEN 'C'
> ELSE 'D'
> END;
> ```

> [accordion] CREATE OR REPLACE should be used instead of CREATE
>
> When creating a function, procedure, package, package body, type, type body, trigger or library, it is a good practice replace the existing one to avoid errors.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE FUNCTION my_function RETURN PLS_INTEGER AS -- Noncompliant
> BEGIN
> RETURN 42;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> CREATE OR REPLACE FUNCTION my_function RETURN PLS_INTEGER AS -- Compliant, no error even if the function already exists
> BEGIN
> RETURN 42;
> END;
> /
> ```

> [accordion] Sensitive SYS owned functions should not be used
>
> Some Oracle packages contain powerful SYS-owned functions that can be used to perform malicious operations. For instance, `DBMS_SYS_SQL.PARSE_AS_USER` can be used to execute a statement as another user.
>
> Most programs do not need those functions and this rule helps identify them in order to prevent security risks.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> c INTEGER;
> sqltext VARCHAR2(100) := 'ALTER USER system IDENTIFIED BY hacker'; -- Might be injected by the user
> BEGIN
> c := SYS.DBMS_SYS_SQL.OPEN_CURSOR();                               -- Noncompliant
>
> -- Will change 'system' user's password to 'hacker'
> SYS.DBMS_SYS_SQL.PARSE_AS_USER(c, sqltext, DBMS_SQL.NATIVE, UID);  -- Non-Compliant
>
> SYS.DBMS_SYS_SQL.CLOSE_CURSOR(c);                                  -- Noncompliant
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] Anchored types should not be constrained
>
> Anchored types, i.e. those specified using either `%TYPE or %ROWTYPE, cannot be constrained. Trying to do so results in the exception PLS-00573: cannot constrain scale, precision, or range of an anchored type being raised.`
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> foo DUAL.DUMMY%TYPE(42); -- Non-Compliant - raises PLS-00573
> BEGIN
> NULL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> foo DUAL.DUMMY%TYPE; -- Compliant
> BEGIN
> NULL;
> END;
> /
> ```

> [accordion] Function and procedure parameters should comply with a naming convention
>
> Each function and procedure parameter name must match a given regular expression.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> FUNCTION myfunction2(parameter_ PLS_INTEGER) RETURN PLS_INTEGER; -- Noncompliant
>
> PROCEDURE myprocedure2(parameter_ PLS_INTEGER); -- Noncompliant
>
> FUNCTION myfunction2(parameter_ PLS_INTEGER) RETURN PLS_INTEGER AS -- Noncompliant
> BEGIN
> RETURN 42;
> END;
>
> PROCEDURE myprocedure2(parameter_ PLS_INTEGER) AS -- Noncompliant
> BEGIN
> NULL;
> END;
> BEGIN
> NULL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> FUNCTION myfunction1(parameter PLS_INTEGER) RETURN PLS_INTEGER; -- Compliant
>
> PROCEDURE myprocedure1(parameter PLS_INTEGER); -- Compliant
>
> FUNCTION myfunction1(parameter PLS_INTEGER) RETURN PLS_INTEGER AS -- Compliant
> BEGIN
> RETURN 42;
> END;
>
> PROCEDURE myprocedure1(parameter PLS_INTEGER) AS -- Compliant
> BEGIN
> NULL;
> END;
>
> BEGIN
> NULL;
> END;
> /
> ```

> [accordion] Cursor parameters should follow a naming convention
>
> Shared coding conventions allow teams to collaborate efficiently. This rule checks that cursor parameters match the provided regular expression.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE TABLE employee(
> name VARCHAR2(42)
> );
>
> DECLARE
> CURSOR mycursor2(Employee-name-parameter_ VARCHAR2) RETURN employee%ROWTYPE; -- Noncompliant
>
> CURSOR mycursor2(Employee-name-parameter_ VARCHAR2) RETURN employee%ROWTYPE IS SELECT * FROM employee WHERE name = Employee-name-parameter_; -- Noncompliant
> BEGIN
> NULL;
> END;
> /
>
> DROP TABLE employee;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> CREATE TABLE employee(
> name VARCHAR2(42)
> );
>
> DECLARE
> CURSOR mycursor2(employeeNameParameter VARCHAR2) RETURN employee%ROWTYPE;
>
> CURSOR mycursor2(employeeNameParameter VARCHAR2) RETURN employee%ROWTYPE IS SELECT * FROM employee WHERE name = employeeNameParameter;
> BEGIN
> NULL;
> END;
> /
>
> DROP TABLE employee;
> ```

> [accordion] Pipelined functions should have at least one PIPE ROW statement and not return an expression (PLS-00633)
>
> Pipelined functions offers the ability to create programmatically generated tables.
>
> One of the benefits of such functions is that they reduce memory consumption as results are not all kept in memory before being returned.
>
> Instead of relying on \`RETURN, PIPE ROW must be used to return the results, one row at a time.
>
> Trying to return an expression from a pipelined function raises PLS-00633: RETURN statement in a pipelined function cannot contain an expression\`
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE OR REPLACE TYPE myScalarType AS OBJECT
> (
> dummy   VARCHAR2(42)
> )
> /
> CREATE OR REPLACE TYPE myTableType AS TABLE OF myScalarType;
> /
>
> CREATE OR REPLACE FUNCTION foo RETURN myTableType PIPELINED AS  -- Noncompliant, should contain at least one PIPE ROW
> result myTableType := myTableType();
> BEGIN
> FOR i IN 1 .. 3 LOOP
> result.EXTEND;
> result(i) := myScalarType('Dummy ' || i);
> END LOOP;
>
> RETURN result;  -- Noncompliant, will raise PLS-00633
> END;
> /
>
> SELECT * FROM TABLE(foo());
>
> DROP FUNCTION foo;
> DROP TYPE myTableType;
> DROP TYPE myScalarType;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> -- ...
>
> CREATE OR REPLACE FUNCTION foo RETURN myTableType PIPELINED AS
> BEGIN
> FOR i IN 1 .. 3 LOOP
> PIPE ROW(myScalarType('Dummy ' || i));
> END LOOP;
>
> RETURN;
> END;
> /
>
> -- ...
> ```

> [accordion] Whitespace and control characters in string literals should be explicit
>
> New lines and control characters can be injected in the source code by bad manipulations. Control characters aren’t visible to maintainers, so whether or not they are actually wanted should be double-checked. Note that this rule can optionally also report violations on literals containing the tabulation character.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> BEGIN
> /* Non-Compliant */ DBMS_OUTPUT.PUT_LINE('Hello
> world!');
>
> DBMS_OUTPUT.PUT_LINE('Hello'); -- Compliant, this is preferred
> DBMS_OUTPUT.PUT_LINE('world!');
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] All code should be reachable
>
> Jump statements (\`EXIT, CONTINUE, RETURN, RAISE, and RAISE\_APPLICATION\_ERROR), move control flow out of the current code block. So any statements that come after a jump are dead code.
>
> This rule detects for statements that follow:
>
> <ul>
>   <li>
>     EXIT without a WHEN
>   </li>
>
>   <li>
>     CONTINUE without a WHEN
>   </li>
>
>   <li>
>     RETURN
>   </li>
>
>   <li>
>     RAISE
>   </li>
>
>   <li>
>     RAISE\_APPLICATION\_ERROR\`
>   </li>
> </ul>
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> BEGIN
> LOOP
> DBMS_OUTPUT.PUT_LINE('This will be printed out');
> EXIT;
>
> DBMS_OUTPUT.PUT_LINE('This will NEVER be printed out'); -- Non-Compliant
> END LOOP;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> BEGIN
> LOOP
> DBMS_OUTPUT.PUT_LINE('This will be printed out');
> EXIT;
> END LOOP;
> END;
> /
> ```

> [accordion] In labeled loops EXIT should exit the label
>
> Labeled loops are useful, especially when the code is badly indented, to match the begin and end of each loop. Within a labeled loop, the code’s maintainability is increased by explicitly providing the loop’s label in every `EXIT` statement. Indeed, if a nested loop is added afterwards, it is clear which loop has to be exited.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> <<myLoopLabel1>>
> LOOP
> EXIT; -- Noncompliant, the loop label is missing
> END LOOP myLoopLabel1;
>
> LOOP
> EXIT; -- Compliant, this EXIT is not in a labeled loop
> END LOOP;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> BEGIN
> <<myLoopLabel1>>
> LOOP
> EXIT myLoopLabel1;
> END LOOP myLoopLabel1;
>
> LOOP
> EXIT;
> END LOOP;
> END;
> /
> ```

> [accordion] An ORDER BY direction should be specified explicitly
>
> `ASC or DESC should be specified for every column of an ORDER BY` clause to improve readability.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> SELECT col1, col2, col3
> BULK COLLECT INTO result
> FROM my_table
> ORDER BY
> col1 ASC,
> col2,            -- Noncompliant - ASC or DESC should be specified
> col3 DESC;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> BEGIN
> SELECT col1, col2, col3
> BULK COLLECT INTO result
> FROM my_table
> ORDER BY
> col1 ASC,
> col2 ASC,
> col3 DESC;
> END;
> /
> ```

> [accordion] CREATE\_TIMER should not be used
>
> `CREATE_TIMER` is generating network traffic each time the timer is fired. It’s probably totally fine for a timer being executed every hour but generally, this is used to provide clocks components that are going to generate network traffic every second or more.
>
> It is recommended by Oracle to examine timers and replace them with JavaBeans.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> timer := CREATE_TIMER('foo', 1000, REPEAR)
> ENDl
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] At least one exception should be handled in an exception block
>
> Shadowing all exceptions with NULL statements indicates that no error handling has been done for a given block of code. This is a common bad-practice and only the non-relevant exceptions should be ignored (and a comment is welcome in such cases).
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN 
> SELECT value 
> INTO :hits 
> FROM hitCounter 
> WHERE pageIn = 'Sample'; 
> EXCEPTION                    -- Noncompliant
> WHEN OTHERS THEN 
> NULL; 
> END; 
>
> BEGIN 
> SELECT value 
> INTO :hits 
> FROM hitCounter 
> WHERE pageIn = 'Sample'; 
> EXCEPTION                    -- Noncompliant
> WHEN TOO_MANY_ROWS THEN
> NULL;
> WHEN OTHERS THEN 
> NULL; 
> END;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> BEGIN 
> SELECT value 
> INTO :hits 
> FROM hitCounter 
> WHERE pageIn = 'Sample'; 
> EXCEPTION                    -- Compliant
> WHEN NO_DATA_FOUND THEN
> hits := 0;
> WHEN TOO_MANY_ROWS THEN
> DBMS_OUTPUT.PUT_LINE('Error: too many entries for Sample');
> WHEN OTHERS THEN 
> -- Cannot do more in this case
> NULL; 
> END;
> ```

> [accordion] NUMBER variables should be declared with precision
>
> Declaring a \`NUMBER variable without any precision wastes memory because Oracle supports up to 38 decimal digits by default (or the maximum supported by your system, whichever is less). If you don’t need that large a value, you should specify whatever matches your needs. This will save memory and provide extra integrity checking on input.
>
> This rule also applies to some NUMBER subtypes as well: NUMERIC, DEC, and DECIMAL\`.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> var1 NUMBER; -- Noncompliant
> var2 NUMERIC; -- Noncompliant
> BEGIN
> NULL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> var1 NUMBER(9,2);
> var2 NUMERIC(4,0);
> BEGIN
> NULL;
> END;
> /
> ```

> [accordion] Loop start and end labels should match
>
> Labeled loops are useful, especially when the code is badly indented, to match the begin and end of each loop. This rule verifies that loop start and end labels match, when both are specified.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> LOOP
> EXIT;
> END LOOP; -- Compliant, this loop has no label at all
>
> <<myLoopLabel1>>
> LOOP
> EXIT;
> END LOOP; -- Compliant, this loop only has a start label
>
> LOOP
> EXIT;
> END LOOP myLoopLabel2; -- Compliant, this loop only has an end label
>
> <<myLoopLabel4>>
> LOOP
> EXIT;
> END LOOP myLoopLabel5; -- Noncompliant, label mismatch
>
> <<myLoopLabel6>>
> <<myLoopLabel7>>
> LOOP
> EXIT;
> END LOOP myLoopLabel7; -- Noncompliant, several start labels mismatch
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> BEGIN
> LOOP
> EXIT;
> END LOOP;
>
> <<myLoopLabel1>>
> LOOP
> EXIT;
> END LOOP;
>
> LOOP
> EXIT;
> END LOOP myLoopLabel2;
>
> <<myLoopLabel4>>
> LOOP
> EXIT;
> END LOOP myLoopLabel4;
>
> <<myLoopLabel7>>
> LOOP
> EXIT;
> END LOOP myLoopLabel7;
> END;
> /
> ```

> [accordion] EXIT WHEN should be used rather than IF ... THEN EXIT; END IF;
>
> The `EXIT WHEN syntax can exit a loop depending on a condition. It should be preferred to the more verbose and error-prone IF ... THEN EXIT; END IF;` syntax.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> i PLS_INTEGER;
> BEGIN
>
> i := 0;
> LOOP
> IF i > 10 THEN -- Noncompliant
>    EXIT;
> END IF;
>
> DBMS_OUTPUT.PUT_LINE('i = ' || i);
> i := i + 1;
> END LOOP;
>
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> i PLS_INTEGER;
> BEGIN
>
> i := 0;
> LOOP
> EXIT WHEN i > 10;
>
> DBMS_OUTPUT.PUT_LINE('i = ' || i);
> i := i + 1;
> END LOOP;
> END;
> /
> ```

> [accordion] IF ... ELSEIF constructs should end with ELSE clauses
>
> This rule applies whenever an \`IF statement is followed by one or
>
> more ELSEIF statements; the final ELSEIF should be followed by an ELSE statement.
>
> The requirement for a final ELSE statement is defensive programming.
>
> The ELSE statement should either take appropriate action or contain
>
> a suitable comment as to why no action is taken. This is consistent with the
>
> requirement to have a final ELSE clause in a CASE\`
>
> statement.
>
> ```plsql Bad theme={"theme":"css-variables"}
> IF my_variable = 0 THEN
> do_something;
> ELSIF my_variable = 1 THEN
> do_something_else;
> END IF;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> IF my_variable = 0 THEN
> do_something;
> ELSIF my_variable = 1 THEN
> do_something_else;
> ELSE
> -- Nothing has to be done.
> NULL;
> END IF;
> ```

> [accordion] Improper constraint forms should not be used
>
> Not every data type supports the `RANGE or scale constraints. Using these constraints on incompatible types results in an PLS-00572: improper constraint form used` exception being raised.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> foo INTEGER RANGE 0 .. 42; -- Non-Compliant - raises PLS-00572 as NUMBER does not support the RANGE constraint
> BEGIN
> NULL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> foo INTEGER; -- Compliant
> BEGIN
> NULL;
> END;
> /
> ```

> [accordion] Assignments of default values for variables should be located in the initialization section
>
> Assigning default values to variables in an initialization section is a good practice as it increases the readability of the code: when starting reading a block, one will know exactly which variables have default values.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> var1 integer;
> var2 integer;
> var3 integer;
> BEGIN
> var1 := 1; -- Noncompliant
> var2 := 2; -- Noncompliant
> var3 := var1 + var2;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> var1 integer := 1;
> var2 integer := 2;
> var3 integer;
> BEGIN
> var3 := var1 + var2;
> END;
> /
> ```

> [accordion] Tables should be aliased
>
> When multiple tables are involved in a query, using table aliases helps to make it more understandable and keeps it short.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> SELECT
> name,
> firstname,
> location
> INTO employeesArray
> FROM employee -- Noncompliant - should be aliased
> INNER JOIN department -- Noncompliant - should be aliased
> ON employee.DepartmentID = department.ID;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> BEGIN
> SELECT
> empl.name,
> empl.firstname,
> dpt.location
> INTO employeesArray
> FROM employee empl
> INNER JOIN department dpt
> ON empl.DepartmentID = dpt.ID;
> END;
> /
> ```

> [accordion] SIMPLE\_INTEGER should be used instead of PLS\_INTEGER
>
> ORACLE 11g introduced the \`SIMPLE\_INTEGER data type, which is a sub-type of PLS\_INTEGER, and covers the same range. There are three main differences between the two types:
>
> <ul>
>   <li>
>     SIMPLE\_INTEGER is always NOT NULL. So when the value of the declared variable is never going to be null, you can declare it as SIMPLE\_INTEGER.
>   </li>
>
>   <li>
>     You will never face a numeric overflow using SIMPLE\_INTEGER because this data type wraps around without giving any error.
>   </li>
>
>   <li>
>     The SIMPLE\_INTEGER data type gives a major performance boost over PLS\_INTEGER when the code is compiled in "NATIVE" mode, because arithmetic operations on SIMPLE\_INTEGER\` type are performed directly at the hardware level.
>   </li>
> </ul>
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> v1 PLS_INTEGER; -- Noncompliant
> v2 VARCHAR2(10);
> BEGIN
> NULL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> v1 SIMPLE_INTEGER := 42;
> v2 VARCHAR2(10);
> BEGIN
> NULL;
> END;
> /
> ```

> [accordion] Unary prefix operators should not be repeated
>
> The repetition of a prefix operator (`+, -, or NOT`) is usually a typo. The second operator invalidates the first one:
>
> ```plsql Bad theme={"theme":"css-variables"}
> IF NOT ( NOT foo = 5 ) THEN  -- Noncompliant: equivalent to "foo = 5"
> value := ++1;              -- Noncompliant: equivalent to "+1"
> END IF;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] ROWNUM should not be used at the same query level as ORDER BY
>
> Oracle’s `ROWNUM is a pseudo column that numbers the rows in a result set. Unfortunately, it numbers the rows in the set before ordering is applied. So combining the two in the same query won’t get you the results you expect. Instead, you should move your selection and ordering into a subquery, and use ROWNUM` only on the outer query.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SELECT fname, lname, deptId
> FROM employee
> WHERE rownum <= 10
> ORDER BY salary  -- Noncompliant
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SELECT * 
> FROM ( SELECT fname, lname, deptId
> FROM employee
> ORDER BY salary
> )
> WHERE rownum <= 10
> ```

> [accordion] END statements of labeled loops should be labeled
>
> Labeled loops are useful, especially when the code is badly indented, to match the begin and end of each loop. This rule raises an issue when the end of a labeled loop is unlabeled.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> <<myLoopLabel1>>
> LOOP
> EXIT;
> END LOOP; -- Noncompliant; this labeled loop has no ending label
>
> LOOP
> EXIT;
> END LOOP; -- Compliant; not a labeled loop
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> BEGIN
> <<myLoopLabel1>>
> LOOP
> EXIT;
> END LOOP myLoopLabel1;
>
> LOOP
> EXIT;
> END LOOP;
> END;
> /
> ```

> [accordion] Names should not be reused in inner scopes
>
> Using the same name for multiple purposes reduces the understandability of the code and might eventually lead to bugs.
>
> This rule verifies that no name is reused in an inner scope.
>
> ```plsql Bad theme={"theme":"css-variables"}
> <<foo>>                                    -- Compliant
> DECLARE
> a CONSTANT PLS_INTEGER := 0;
> BEGIN
> <<foo>>                                  -- Non-Compliant
> DECLARE
> b CONSTANT PLS_INTEGER := 42;
> BEGIN
> DBMS_OUTPUT.PUT_LINE('x = ' || foo.b); -- Confusing
> END;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> <<foo>>                                    -- Compliant
> DECLARE
> a CONSTANT PLS_INTEGER := 0;
> BEGIN
> <<bar>>                                  -- Compliant
> DECLARE
> b CONSTANT PLS_INTEGER := 42;
> BEGIN
> DBMS_OUTPUT.PUT_LINE('x = ' || bar.b); -- Clear
> END;
> END;
> /
> ```

> [accordion] Global public variables should not be defined
>
> When data structures (scalar variables, collections, cursors) are declared in the package specification (not within any specific program), they can be referenced directly by any program running in a session with `EXECUTE` rights to the package.
>
> Instead, declare all package-level data in the package body and provide getter and setter functions in the package specification. Developers can then access the data using these methods and will automatically follow all rules you set upon data modification.
>
> By doing so you can guarantee data integrity, change your data structure implementation, and also track access to those data structures.
>
> ```plsql Bad theme={"theme":"css-variables"}
> -- Package specification
> CREATE PACKAGE employee AS
> name VARCHAR2(42); -- Non-Compliant
> END employee;
> /
>
> DROP PACKAGE employee;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> -- Package specification
> CREATE PACKAGE employee AS
> PROCEDURE setName (newName VARCHAR2);
> FUNCTION getName RETURN VARCHAR2;
> END employee;
> /
>
> -- Package body
> CREATE PACKAGE BODY employee AS
> name VARCHAR2(42);
>
> PROCEDURE setName (newName VARCHAR2) IS
> BEGIN
>  name := newName;
> END;
>
> FUNCTION getName RETURN VARCHAR2 IS
> BEGIN
>  RETURN name;
> END;
> END employee;
> /
>
> DROP PACKAGE BODY employee;
>
> DROP PACKAGE employee;
> ```

> [accordion] Native SQL joins should be used
>
> SQL is an extremely powerful and hard to master language. It may be tempting to emulate SQL joins in PL/SQL using nested cursor loops, but those are not optimized by Oracle at all. In fact, they lead to numerous context switches between the SQL and PL/SQL engines, and those switches have a highly negative impact on performance. It is therefore much better to replace nested PL/SQL cursor loops with native SQL joins.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> CREATE TABLE countriesTable(
> countryName VARCHAR2(42)
> );
>
> CREATE TABLE citiesTable(
> cityName VARCHAR2(42)
> );
>
> INSERT INTO countriesTable VALUES('India');
> INSERT INTO countriesTable VALUES('Switzerland');
> INSERT INTO countriesTable VALUES('United States');
>
> INSERT INTO citiesTable VALUES('Berne');
> INSERT INTO citiesTable VALUES('Delhi');
> INSERT INTO citiesTable VALUES('Bangalore');
> INSERT INTO citiesTable VALUES('New York');
>
> BEGIN
> FOR countryRecord IN (SELECT countryName FROM countriesTable) LOOP
> FOR cityRecord IN (SELECT cityName FROM citiesTable) LOOP -- Non-Compliant
>   DBMS_OUTPUT.PUT_LINE('Country: ' || countryRecord.countryName || ', City: ' || cityRecord.cityName);
> END LOOP;
> END LOOP;
> END;
> /
>
> DROP TABLE citiesTable;
>
> DROP TABLE countriesTable;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> CREATE TABLE countriesTable(
> countryName VARCHAR2(42)
> );
>
> CREATE TABLE citiesTable(
> cityName VARCHAR2(42)
> );
>
> INSERT INTO countriesTable VALUES('India');
> INSERT INTO countriesTable VALUES('Switzerland');
> INSERT INTO countriesTable VALUES('United States');
>
> INSERT INTO citiesTable VALUES('Berne');
> INSERT INTO citiesTable VALUES('Delhi');
> INSERT INTO citiesTable VALUES('Bangalore');
> INSERT INTO citiesTable VALUES('New York');
>
> BEGIN
> FOR myRecord IN (SELECT * FROM countriesTable CROSS JOIN citiesTable) LOOP -- Compliant
> DBMS_OUTPUT.PUT_LINE('Country: ' || myRecord.countryName || ', City: ' || myRecord.cityName);
> END LOOP;
> END;
> /
>
> DROP TABLE citiesTable;
>
> DROP TABLE countriesTable;
> ```

> [accordion] EXCEPTION WHEN ... THEN clauses should do more than RAISE
>
> An `EXCEPTION WHEN ... THEN clause that only rethrows the caught exception has the same effect as omitting the EXCEPTION` clause altogether and letting it bubble up automatically.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> SELECT 1/0;
> EXCEPTION
> WHEN ZERO_DIVIDE THEN
> RAISE; -- Noncompliant
> WHEN OTHERS THEN
> RAISE; -- Noncompliant
> END;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> BEGIN
> SELECT 1/0;
> EXCEPTION
> WHEN ZERO_DIVIDE THEN
> -- do something to manage the division by zero
> COMMIT;
>
> WHEN OTHERS THEN
> ROLLBACK;
> END;
> ```

> [accordion] Columns should be aliased
>
> Consistently using aliases for column names is useful for several reasons. The main one is that the code is independant from potential database modifications - when a column has been renamed to comply with standards for instance. Another reason is to remove ambiguity when querying several tables that may have equivalent column names.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> SELECT
> emp.name, -- Noncompliant - should be aliased
> dpt.name -- Noncompliant - should be aliased
> INTO employeesArray
> FROM employee emp INNER JOIN department dpt
> ON emp.DepartmentID = dpt.ID;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> BEGIN
> SELECT
> emp.name employee_name, -- Compliant
> dpt.name departement_name -- Compliant
> INTO employeesArray
> FROM employee emp INNER JOIN department dpt
> ON emp.DepartmentID = dpt.ID;
> END;
> /
> ```

> [accordion] Positional and named arguments should not be mixed in invocations
>
> For better readability, and to prevent the `PLS-00312: a positional parameter association may not follow a named association` exception from being raised, do not mix named and positional argument invocations.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> PROCEDURE sub(op1 PLS_INTEGER, op2 PLS_INTEGER) AS
> BEGIN
> DBMS_OUTPUT.PUT_LINE('Sub = ' || (op1 - op2));
> END;
> BEGIN
>
> sub(10, op2 => 2); -- Noncompliant
> sub(op1 => 10, 2); -- Noncompliant - raises PLS-00312: a positional parameter association may not follow a named association
>
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> PROCEDURE sub(op1 PLS_INTEGER, op2 PLS_INTEGER) AS
> BEGIN
> DBMS_OUTPUT.PUT_LINE('Sub = ' || (op1 - op2));
> END;
> BEGIN
>
> sub(10, 2); -- Compliant
> sub(op1 => 10, op2 => 2); -- Compliant
>
> END;
> /
> ```

> [accordion] Variables should be declared only once in a scope
>
> At most one declaration of a variable in a given scope is allowed in PL/SQL. The `PLS-00371` error will be raised at runtime when attempting to reference a variable declared more than once.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> foo VARCHAR2(42) := 'foo';
> foo VARCHAR2(42) := 'bar'; -- Non-Compliant
> BEGIN
> DBMS_OUTPUT.PUT_LINE(foo); -- Raises PLS-00371: at most one declaration for 'FOO' is permitted
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> foo VARCHAR2(42) := 'foo';
> bar VARCHAR2(42) := 'bar'; -- Compliant
> BEGIN
> DBMS_OUTPUT.PUT_LINE(foo);
> END;
> /
> ```

> [accordion] The result\_cache hint should be avoided
>
> The `result_cache` Oracle hint can vastly improve performance, but it comes at the cost of extra memory consumption, so one should double-check that the gain in performance is significant, and avoid overusing this feature in general.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SELECT /*+ result_cache */ * FROM DUAL;  -- Noncompliant
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] Compound triggers should define at least two triggers
>
> Compound triggers were introduced to ease the implementation of multiple triggers which need to work in cooperation.
>
> Typically, a \`FOR EACH ROW trigger accumulates facts, and an AFTER STATEMENT trigger performs the actual changes.
>
> The compound trigger can hold a state common to all the triggers it defines, thereby removing the need to use package variables. This approach is sometimes the only possible one, as when avoiding a mutating table ORA-04091\` error, or it can be used to get better performance.
>
> However, there is no point in defining a compound trigger which contains only a single trigger, since there is no state to be shared. In such cases, a simple trigger should be used instead.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE OR REPLACE TRIGGER my_trigger  -- Noncompliant; defines a single trigger
> FOR INSERT ON my_table
> COMPOUND TRIGGER
>
> AFTER EACH ROW IS
> BEGIN
> DBMS_OUTPUT.PUT_LINE('New row inserted!');
> END AFTER EACH ROW;
>
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> CREATE OR REPLACE TRIGGER my_trigger
> AFTER INSERT
> ON my_table
> FOR EACH ROW
> BEGIN
> DBMS_OUTPUT.PUT_LINE('New row inserted!');
> END;
> /
> ```

> [accordion] Reserved words should be written in lower case
>
> All reserved words should be written using the same case to ensure consistency in the code.
>
> This rule checks that reserved words are all in lower case.
>
> ```plsql Bad theme={"theme":"css-variables"}
> begin
> null;
> NULL; -- Noncompliant
> end;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] Variables should not be declared inside loops
>
> It is a best practice to have variable declarations outside of the loop. Additionally, declaring variables inside a loop is slightly less efficient because memory management is then performed with each iteration of the loop.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> FOR i IN 1..10 
> LOOP
> DECLARE
>   variableX NUMBER:= 10;
> BEGIN
>     variableX:= variableX+i;
>     dbms_output.put_line(variableX);
> END;
> END LOOP;
> END;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> variableX NUMBER:= 0;
> BEGIN
> FOR i IN 1..10
> LOOP
> variableX:= variableX+1;
> dbms_output.put_line(variableX);
> END LOOP;
> END;
> ```

> [accordion] %TYPE and %ROWTYPE should not be used in package specification
>
> \`%TYPE and %ROWTYPE seem like an easy way to make sure that a variable’s type always matches the type of the relevant column in an existing table. If the column type changes, then the variable changes with it.
>
> However, Oracle Forms compiled against a procedure using either of these two symbols won’t get the benefit of that flexibility. Instead, at compile time, the relevant type is looked up from the underlying database and used in the form. If the column type changes later or the form is running against a database with different length semantics, attempting to use the form results in an "ORA-04062: Signature of package has been changed" error on the package in question. And the form needs to be recompiled on exactly the same database environment where it will run to avoid the error.
>
> Note that %TYPE and %ROWTYPE\` can be used in a package’s private procedures and functions, private package variables, and local variables without issue, but not in the package specification.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE OR REPLACE PACKAGE PACK IS
> TYPE mytype IS RECORD (
> var1 mytable.mycolumn%TYPE -- Noncompliant
> );
>
> FUNCTION MY_FUNC(param1 IN mytable.mycolumn%TYPE) RETURN VARCHAR2; -- Noncompliant
>
> FUNCTION MY_FUNC2(param1 IN mytable%ROWTYPE) RETURN VARCHAR2; -- Noncompliant
>
> END;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> CREATE OR REPLACE PACKAGE PACK IS
> TYPE mytype IS RECORD (
> var1 VARCHAR2(100) -- Compliant
> );
>
> FUNCTION MY_FUNC(param1 IN VARCHAR2) RETURN VARCHAR2; -- Compliant
>
> TYPE myrowtype IS RECORD (
> col1 NUMBER,
> col2 VARCHAR2(30)
> );
> FUNCTION MY_FUNC2(param1 IN myrowtype) RETURN VARCHAR2; -- Compliant
>
> END;
> ```

> [accordion] Nested blocks should be labeled
>
> Labeled blocks are useful, especially when the code is badly indented, to help maintainers match the beginning and ending of each block. When blocks are nested, labeling them can improve the code’s readability. This rule detects nested block which do not have a start label.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN -- Compliant, this is not a nested block
> NULL;
> END;
> /
>
> BEGIN
> BEGIN -- Noncompliant; this nested block has no label
> NULL;
> END;
> END;
> /
>
> BEGIN
> BEGIN -- Noncompliant; this nested block has only an end label
> NULL;
> END myBlockLabel1;
>
> <<myBlockLabel2>> -- Compliant
> BEGIN
> NULL;
> END;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> BEGIN 
> NULL;
> END;
> /
>
> BEGIN
> BEGIN myBlockLabel0
> NULL;
> END myBlockLabel0;
> END;
> /
>
> BEGIN
> BEGIN myBlockLabel1
> NULL;
> END myBlockLabel1;
>
> <<myBlockLabel2>>
> BEGIN
> NULL;
> END;
> END;
> /
> ```

> [accordion] Cursors should follow a naming convention
>
> Shared coding conventions allow teams to collaborate efficiently. This rule checks that all cursor names match the provided regular expression.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE TABLE employee(
> name VARCHAR2(42)
> );
>
> DECLARE
> CURSOR myCursor_ RETURN employee%ROWTYPE; -- Noncompliant
>
> CURSOR myCursor_ RETURN employee%ROWTYPE IS SELECT * FROM employee; -- Noncompliant
> BEGIN
> NULL;
> END;
> /
>
> DROP TABLE employee;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> CREATE TABLE employee(
> name VARCHAR2(42)
> );
>
> DECLARE
> CURSOR myCursor RETURN employee%ROWTYPE;
>
> CURSOR myCursor RETURN employee%ROWTYPE IS SELECT * FROM employee;
> BEGIN
> NULL;
> END;
> /
>
> DROP TABLE employee;
> ```

> [accordion] COMMIT and ROLLBACK should not be called from non-autonomous transaction triggers
>
> Calling `COMMIT or ROLLBACK from within a trigger will lead to an ORA-04092` exception, unless the trigger has its own autonomous transaction.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> CREATE TABLE accounts(
> balance NUMBER
> );
>
> INSERT INTO accounts VALUES(0);
>
> CREATE TABLE log(
> message VARCHAR2(100)
> );
>
> CREATE TRIGGER beforeLogger
> BEFORE UPDATE ON accounts
> FOR EACH ROW
> BEGIN
> INSERT INTO log VALUES('Attempt to update the value from ' || :OLD.balance || ' to ' || :NEW.balance);
> COMMIT; -- Noncompliant, will fail with a ORA-04092
> END;
> /
>
> -- We want to be able to log any attempt to update the "accounts" table
> BEGIN
> UPDATE accounts SET balance = 100;
> ROLLBACK; -- Ultimately, this update is rolled back, however we still want to log it
> END;
> /
>
> SELECT * FROM log;
>
> DROP TRIGGER beforeLogger;
>
> DROP TABLE log;
>
> DROP TABLE accounts;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> CREATE TABLE accounts(
> balance NUMBER
> );
>
> INSERT INTO accounts VALUES(0);
>
> CREATE TABLE log(
> message VARCHAR2(100)
> );
>
> CREATE TRIGGER beforeLogger
> BEFORE UPDATE ON accounts
> FOR EACH ROW
> DECLARE
> PRAGMA AUTONOMOUS_TRANSACTION;
> BEGIN
> INSERT INTO log VALUES('Attempt to update the value from ' || :OLD.balance || ' to ' || :NEW.balance);
> COMMIT; -- Compliant, commits the trigger's autonomous transaction, not the main one
> END;
> /
>
> -- We want to be able to log any attempt to update the "accounts" table
> BEGIN
> UPDATE accounts SET balance = 100;
> ROLLBACK; -- Ultimately, this update is rolled back, however we still want to log it
> END;
> /
>
> SELECT * FROM log;
>
> DROP TRIGGER beforeLogger;
>
> DROP TABLE log;
>
> DROP TABLE accounts;
> ```

> [accordion] Variables should be nullable
>
> Declaring a variable with the NOT NULL constraint incurs a small performance cost - while this constraint may not really be required. Using such a constraint should be avoided.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> counter PLS_INTEGER NOT NULL := 0; -- Noncompliant
> BEGIN
> NULL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> counter PLS_INTEGER := 0; -- Compliant
> BEGIN
> NULL;
> END;
> /
> ```

> [accordion] FETCH ... BULK COLLECT INTO should not be used without a LIMIT clause
>
> A `FETCH ... BULK COLLECT INTO without a LIMIT clause will load all the records returned by the cursor at once. This may lead to memory exhaustion. Instead, it is better to process the records in chunks using the LIMIT` clause.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> -- Fetches all records at once, requiring lots of memory
> DECLARE
> TYPE largeTableRowArrayType IS TABLE OF largeTable%ROWTYPE;
> largeTableRowArray largeTableRowArrayType;
> CURSOR myCursor IS SELECT * FROM largeTable;
> BEGIN
> OPEN myCursor;
>
> FETCH myCursor BULK COLLECT INTO largeTableRowArray; -- Non-compliant
>
> DBMS_OUTPUT.PUT_LINE('Alternative 1: ' || largeTableRowArray.COUNT || ' records');
>
> CLOSE myCursor;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> -- fetches one chunk at a time, requiring constant memory
> DECLARE
> TYPE largeTableRowArrayType IS TABLE OF largeTable%ROWTYPE;
> largeTableRowArray largeTableRowArrayType;
> CURSOR myCursor IS SELECT * FROM largeTable;
> counter PLS_INTEGER := 0;
> BEGIN
> OPEN myCursor;
>
> LOOP
> FETCH myCursor BULK COLLECT INTO largeTableRowArray LIMIT 1000; -- Compliant
>
> counter := counter + largeTableRowArray.COUNT;
>
> EXIT WHEN myCursor%NOTFOUND;
> END LOOP;
>
> DBMS_OUTPUT.PUT_LINE('Alternative 1: ' || counter || ' records');
>
> CLOSE myCursor;
> END;
> /
>
> DROP TABLE largeTable;
> ```

> [accordion] DBMS\_UTILITY.FORMAT\_ERROR\_STACK and FORMAT\_ERROR\_BACKTRACE should be used together
>
> Since Oracle 10g, `DBMS_UTILITY.FORMAT_ERROR_BACKTRACE is available to get an exception’s stack trace, i.e. files and lines that lead up to the exception. When combined with DBMS_UTILITY.FORMAT_ERROR_STACK`, which contains the exception error code and message, developers are able quickly identify defects.
>
> This rule verifies that whenever either is used in an exception handler, the other is used as well.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> RAISE_APPLICATION_ERROR(-20000, 'This is an error example');
> EXCEPTION
> WHEN OTHERS THEN  -- Noncompliant; only FORMAT_ERROR_STACK is used
> DBMS_OUTPUT.PUT(DBMS_UTILITY.FORMAT_ERROR_STACK);           -- "ORA-20000: This is an error example"
> DBMS_OUTPUT.PUT_LINE('');
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> BEGIN
> RAISE_APPLICATION_ERROR(-20000, 'This is an error example');
> EXCEPTION
> WHEN OTHERS THEN
> DBMS_OUTPUT.PUT(DBMS_UTILITY.FORMAT_ERROR_STACK);           -- "ORA-20000: This is an error example"
> DBMS_OUTPUT.PUT(DBMS_UTILITY.FORMAT_ERROR_BACKTRACE);       -- "ORA-06512: at line 2"
> DBMS_OUTPUT.PUT_LINE('');
> END;
> /
> ```

> [accordion] GOTO statements should not be used
>
> A `GOTO` statement is an unstructured change in the control flow. They should be avoided and replaced by structured constructs.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> i PLS_INTEGER := 42;
> BEGIN
> IF i < 0 THEN
> GOTO negative; -- Noncompliant
> END IF;
>
> DBMS_OUTPUT.PUT_LINE('positive');
> goto cleanup; -- Noncompliant
>
> <<negative>>
> DBMS_OUTPUT.PUT_LINE('negative!');
>
> <<cleanup>>
> NULL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> i PLS_INTEGER := 42;
> BEGIN
> IF i < 0 THEN
> DBMS_OUTPUT.PUT_LINE('negative!'); -- Compliant
> ELSE
> DBMS_OUTPUT.PUT_LINE('positive');
> END IF;
> END;
> /
> ```

> [accordion] Scale should not be specified for float types
>
> Float data types, such as `FLOAT, DOUBLE PRECISION, and REAL cannot have a scale constraint. Trying to specify a scale results in the exception PLS-00510: Float cannot have scale being raised.`
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> foo FLOAT(10, 3); -- Noncompliant - raises PLS-00510
> BEGIN
> NULL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> foo FLOAT(10); -- Compliant
> BEGIN
> NULL;
> END;
> /
> ```

> [accordion] Reserved words should be written in upper case
>
> Shared coding conventions allow teams to collaborate efficiently. This rule checks that reserved words are written in upper case.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> null; -- Noncompliant
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> BEGIN
> NULL;
> END;
> /
> ```

> [accordion] FORALL statements should use the SAVE EXCEPTIONS clause
>
> When the `FORALL statement is used without the SAVE EXCEPTIONS clause and an exception is raised by a DML query, the whole operation is rolled back and the exception goes unhandled. Instead of relying on this default behavior, it is better to always use the SAVE EXCEPTIONS clause and explicitly handle exceptions in a ORA-24381` handler.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE TABLE my_table(
> id NUMBER(10) NOT NULL
> );
>
> DECLARE
> TYPE my_table_id_type IS TABLE OF my_table.id%TYPE;
> my_table_ids my_table_id_type := my_table_id_type();
> BEGIN
> FOR i IN 1 .. 10 LOOP
> my_table_ids.EXTEND;
> my_table_ids(my_table_ids.LAST) := i;
> END LOOP;
>
> -- Cause the failure
> my_table_ids(10) := NULL;
>
> FORALL i IN my_table_ids.FIRST .. my_table_ids.LAST  -- Noncompliant
> INSERT INTO my_table
> VALUES (my_table_ids(i));
> END;
> /
>
> SELECT COUNT(*) FROM my_table;
>
> DROP TABLE my_table;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> -- ...
>
> DECLARE
> TYPE my_table_id_type IS TABLE OF my_table.id%TYPE;
> my_table_ids my_table_id_type := my_table_id_type();
>
> bulk_errors EXCEPTION;
> PRAGMA EXCEPTION_INIT(bulk_errors, -24381);
> BEGIN
> FOR i IN 1 .. 10 LOOP
> my_table_ids.EXTEND;
> my_table_ids(my_table_ids.LAST) := i;
> END LOOP;
>
> -- Cause the failure
> my_table_ids(10) := NULL;
>
> FORALL i IN my_table_ids.FIRST .. my_table_ids.LAST SAVE EXCEPTIONS
> INSERT INTO my_table
> VALUES (my_table_ids(i));
> EXCEPTION
> WHEN bulk_errors THEN
> -- Explicitly rollback the whole transaction,
> -- or handle each exception individually by looping over SQL%BULK_EXCEPTIONS
> ROLLBACK;
> END;
> /
>
> -- ...
> ```

> [accordion] ROWID and UROWID data types should not be used
>
> Be careful about your use of Oracle-specific data types like \`ROWID and UROWID. They might offer a slight improvement in performance over other means of identifying a single row (primary key or unique index value), but that is by no means guaranteed.
>
> On the other hand, the use of ROWID or UROWID\` means that your SQL statement will not be portable to other SQL databases. Further, many developers are not familiar with these data types, which can make the code harder to maintain.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> id rowid; -- Non-Compliant
> universeId urowid; -- Non-Compliant
> BEGIN
> SELECT rowid INTO id FROM DUAL;
> SELECT rowid INTO universeId FROM DUAL;
>
> DBMS_OUTPUT.PUT_LINE('id = ' || id);
> DBMS_OUTPUT.PUT_LINE('universe id = ' || universeId);
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] Weak REF CURSOR types should not be used
>
> Weak \`REF CURSOR types are harder to work with than ones with a return type. Indeed, the compiler’s type-checker is unable to make some verifications, which are then delayed till runtime.
>
> When the use of weak REF CURSOR is required, it is best to use the SYS\_REFCURSOR built-in type instead of defining a new one.
>
> This rule’s sysRefCursorAllowed parameter can be used to control whether or not the usage of SYS\_REFCURSOR\` is allowed.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> TYPE dualCursorType IS REF CURSOR;                      -- Noncompliant
> dualCursor dualCursorType;
>
> otherCursor SYS_REFCURSOR;                              -- Compliant or non-compliant, depending on the "sysRefCursorAllowed" parameter
> BEGIN
> otherCursor := dualCursor;                              -- Works
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> TYPE dualCursorType IS REF CURSOR RETURN DUAL%ROWTYPE;
> dualCursor dualCursorType;
>
> TYPE otherCursorType IS REF CURSOR RETURN a%ROWTYPE;
> otherCursor otherCursorType;
> BEGIN
> otherCursor := dualCursor;                              -- raises PLS-00382: expression is of wrong type, which makes debugging easier
> END;
> /
> ```

> [accordion] Blocks containing EXECUTE IMMEDIATE should trap all exceptions
>
> Since the purpose of the `EXECUTE IMMEDIATE` statement is to execute dynamic SQL queries - which by definition can contain unexpected errors - properly handling exceptions becomes critical. Therefore, care should be taken to trap all possible exceptions.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> result      VARCHAR2(42);
> column      VARCHAR2(42);
> BEGIN
> column := 'DUMMY_2';
> EXECUTE IMMEDIATE 'SELECT ' || column || ' FROM DUAL' INTO result; -- Non-Compliant
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> result      VARCHAR2(42);
> column      VARCHAR2(42);
> BEGIN
> column := 'DUMMY_2';
> EXECUTE IMMEDIATE 'SELECT ' || column || ' FROM DUAL' INTO result; -- Compliant
> EXCEPTION
> WHEN OTHERS THEN
> DBMS_OUTPUT.PUT_LINE ('Execute immediate error: ' || DBMS_UTILITY.FORMAT_ERROR_STACK);
> END;
> /
> ```

> [accordion] Strings should only be moved to variables or columns which are large enough to hold them
>
> Trying to assign a large character value to a smaller variable or column will raise an error.
>
> ```plsql Bad theme={"theme":"css-variables"}
> create table persons (id number, name varchar2(4));
>
> insert into persons (id, name) values (1, 'Alice'); -- Noncompliant, raises ORA-12899
>
> create or replace procedure sp1
> is 
> foo varchar2(2);
> begin
> select name into foo from persons where id = 1; -- Noncompliant, may raise ORA-06502
> end;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> create table persons (id number, name varchar2(8));
>
> insert into persons (id, name) values (1, 'Alice');
>
> create or replace procedure sp1
> is 
> foo varchar2(8);
> begin
> select name into foo from persons where id = 1;
> end;
> ```

> [accordion] WHEN clauses should not have too many lines
>
> The `CASE statement should be used only to clearly define some new branches in the control flow. As soon as a WHEN clause contains too many statements this highly decreases the readability of the overall control flow statement. In such case, the content of WHEN` clause should be extracted in a dedicated function.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CASE my_variable
> WHEN 0 THEN -- 6 lines till next WHEN
> procedure1;
> procedure2;
> procedure3;
> procedure4;
> procedure5;
> WHEN 1 THEN
> -- ...
> END CASE;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> PROCEDURE do_something AS
> BEGIN
> procedure1;
> procedure2;
> procedure3;
> procedure4;
> procedure5;
> END;
> BEGIN
> CASE my_variable
> WHEN 0 THEN
>   do_something;
> WHEN 1 THEN
> -- ...
> END CASE;
> END;
> /
> ```

> [accordion] Single-line comments should not be used
>
> From the Oracle docs:
>
> > Do not put a single-line comment in a PL/SQL block that will be processed dynamically by an Oracle Precompiler program. The Oracle Precompiler program ignores end-of-line characters, which means that a single-line comment will end at the end of the block.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> howmany     NUMBER;
> num_tables  NUMBER;
> BEGIN
> -- Begin processing
> SELECT COUNT(*) INTO howmany
> FROM USER_OBJECTS
>   WHERE OBJECT_TYPE = 'TABLE'; -- Check number of tables
> num_tables := howmany;          -- Compute some other value
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> howmany     NUMBER;
> num_tables  NUMBER;
> BEGIN
> /* Begin processing */
> SELECT COUNT(*) INTO howmany
> FROM USER_OBJECTS
>   WHERE OBJECT_TYPE = 'TABLE'; 
> num_tables := howmany;
> END;
> /
> ```

> [accordion] All branches in a conditional structure should not have exactly the same implementation
>
> Having all branches of a CASE or IF/ELSIF chain with the same implementation indicates a problem.
>
> In the following code:
>
> ```plsql Bad theme={"theme":"css-variables"}
> IF param = 1 THEN
> result := 'A';
> ELSIF param = 2 THEN
> result := 'A';
> ELSE
> result := 'A';
> END IF;
>
> result := CASE param
> WHEN 1 THEN 'A'
> WHEN 2 THEN 'A'
> ELSE 'A'
> END;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> IF param = 1 THEN   -- no issue, this could have been done on purpose to make the code more readable
> result := 'A';
> ELSIF param = 2 THEN
> result := 'A';
> END IF;
> ```

> [accordion] Variables should not be initialized with NULL
>
> Explicit variable initializations with null values are superfluous, since unassigned variables are implicitly initialized to null.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> foo PLS_INTEGER := NULL; -- Noncompliant, the null assignation is superfluous
> bar VARCHAR2(100) := ''; -- Noncompliant, the null assignation is superfluous
> correctInitializedString VARCHAR2(100) := 'Hello world!';
>
> BEGIN
> IF foo IS NULL THEN
> DBMS_OUTPUT.PUT_LINE('foo is NULL');
> ELSE
> DBMS_OUTPUT.PUT_LINE('foo is NOT NULL');
> END IF;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> foo PLS_INTEGER;
> bar VARCHAR2(100);
> correctInitializedString VARCHAR2(100) := 'Hello world!';
>
> BEGIN
> IF foo IS NULL THEN
> DBMS_OUTPUT.PUT_LINE('foo is NULL');
> ELSE
> DBMS_OUTPUT.PUT_LINE('foo is NOT NULL');
> END IF;
> END;
> /
> ```

> [accordion] Block labels should appear on the same lines as END
>
> Labeled blocks are useful to help maintainers match-up the beginning and ending of each section of code, especially when that code is badly indented. However, if used, those labels must appear on the same line as the "END" keyword in order to avoid confusion. Otherwise, the label might be misread by maintainers as a procedure call.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> PROCEDURE foo AS
> BEGIN
> DBMS_OUTPUT.PUT_LINE('foo was called!');
> END;
> BEGIN
> BEGIN
> NULL;
> END -- Semicolon was forgotten?
>
> foo; -- Noncompliant; looks like a procedure call, but is actually END block label
>
> <<myBlockLabel>>
> BEGIN
> NULL;
> END 
> myBlockLabel; -- Noncompliant
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> PROCEDURE foo AS
> BEGIN
> DBMS_OUTPUT.PUT_LINE('foo was called!');
> END;
> BEGIN
> BEGIN
> NULL;
> END; 
>
> foo; -- The method "foo" was actually meant to be called
>
> <<myBlockLabel>>
> BEGIN
> NULL;
> END myBlockLabel;
> END;
> /
> ```

> [accordion] VARCHAR2 should be used
>
> Currently, VARCHAR and VARCHAR2 are identical data types. But to prevent future changes in behavior, Oracle recommends the use of VARCHAR2.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> var VARCHAR(42);  -- Noncompliant
> BEGIN
> NULL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> var VARCHAR2(42);  -- Compliant
> BEGIN
> NULL;
> END;
> /
> ```

> [accordion] NCHAR and NVARCHAR2 size should not be specified in bytes
>
> `NCHAR and NVARCHAR2 lengths must be given in characters, not bytes. This is partly because a single character may occupy more than a single byte in memory. Specify the field length in bytes, and theoretically your value could overrun the field, but instead Oracle simply refuses to run the code. Specify it in characters, and Oracle will allocate the appropriate number of bytes to store the requested number of characters. Trying to specify the length semantics in bytes will result in the PLS-00639: NCHAR/NVARCHAR2 cannot be byte length semantics` exception being raised.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> foo NCHAR(42 BYTE); -- Noncompliant - raises PLS-00639
> BEGIN
> NULL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> foo NCHAR(42);      -- Compliant
> bar NCHAR(42 CHAR); -- Also compliant, as an alternative
> BEGIN
> NULL;
> END;
> /
> ```

> [accordion] Functions should end with RETURN statements
>
> Always having a `RETURN as the last statement in a function is a good practice as it prevents the ORA-06503 PL/SQL: Function returned without value` error.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE FUNCTION incorrectFunction RETURN PLS_INTEGER IS -- Non-Compliant
> BEGIN
> NULL; -- This function was expected to return a PLS_INTEGER, but did not. Will lead to ORA-06503
> END;
> /
>
> BEGIN
> DBMS_OUTPUT.PUT_LINE('Ret = ' || incorrectFunction2); -- ORA-06503 PL/SQL: Function returned without value
> END;
> /
>
> DROP FUNCTION incorrectFunction;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> CREATE FUNCTION correctFunction RETURN PLS_INTEGER IS -- Compliant
> BEGIN
> RETURN 42;
> END;
> /
>
> DROP FUNCTION correctFunction;
> ```

> [accordion] EXCEPTION\_INIT -20,NNN calls should be centralized
>
> Centralizing the definitions of custom exceptions comes with two major benefits:
>
> <ul>
>   <li>
>     The duplication of the exceptions declarations and `PRAGMA EXCEPTION_INIT` is avoided
>   </li>
>
>   <li>
>     The risk of associating multiple different exceptions to the same number is reduced
>   </li>
> </ul>
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> user_not_found EXCEPTION;
> PRAGMA EXCEPTION_INIT(user_not_found, -20000); -- Noncompliant, user_not_found is bound to -20000
> BEGIN
> NULL;
> END;
> /
>
> DECLARE
> user_not_found EXCEPTION;
> PRAGMA EXCEPTION_INIT(user_not_found, -20000); -- Noncompliant, user_not_found is again bound to -20000, duplication
> BEGIN
> NULL;
> END;
> /
>
> DECLARE
> wrong_password EXCEPTION;
> PRAGMA EXCEPTION_INIT(wrong_password, -20000); -- Noncompliant, wrong_password is bound to -20000, conflicting with user_not_found
> BEGIN
> NULL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> CREATE PACKAGE exceptions AS
> user_not_found EXCEPTION;
> wrong_password EXCEPTION;
>
> PRAGMA EXCEPTION_INIT(user_not_found, -20000); -- Non-Compliant (flag as false-positive)
> PRAGMA EXCEPTION_INIT(wrong_password, -20001); -- Non-Compliant (flag as false-positive), conflicts are easier to avoid
> END;
> /
>
> DROP PACKAGE exceptions;
> ```

> [accordion] PLS\_INTEGER types should be used
>
> Using a \`NUMBER to store an integer is less performant than using a PLS\_INTEGER. PLS\_INTEGERs require less storage than NUMBERs, and benefit from the use of hardware math, as opposed to the library math required for NUMBERs. Even more performant is the SIMPLE\_INTEGER subtype of PLS\_INTEGER. However, changing to either of these types is only appropriate under certain circumstances.
>
> PLS\_INTEGER is only a candidate for NUMBER with a scale of up to 9.
>
> SIMPLE\_INTEGER has the same size limitation, in addition to it’s NOT NULL constraint and lack of overflow checking.
>
> This rule raises an issue when a NUMBER\` is declared with a scale of 9 or less.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> son NUMBER(1);      -- Noncompliant
> rumbo NUMBER(9);  -- Noncompliant
> conga Number(10);   -- Ignored; falls outside the PLS_INTEGER range
> compalsa PLS_INTEGER;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> son SIMPLE_INTEGER;
> rumbo PLS_INTEGER;
> conga Number(10);   -- Ignored; falls outside the PLS_INTEGER range
> compalsa PLS_INTEGER;
> ```

> [accordion] LOOP ... END LOOP; constructs should be avoided
>
> Simple loops, of the form `LOOP ... END LOOP`, behave by default as infinite ones, since they do not have a loop condition. They can often be replaced by other, safer, loop constructs.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> i PLS_INTEGER;
> BEGIN
> i := 1;
> LOOP -- Noncompliant, an infinite loop by default and therefore dangerous
> DBMS_OUTPUT.PUT_LINE('First loop i: ' || i);
>
> i := i + 1;
> EXIT WHEN i > 10;
> END LOOP;
>
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> i PLS_INTEGER;
> BEGIN
> FOR i IN 1..10 LOOP -- Compliant, much safer equivalent alternative
> DBMS_OUTPUT.PUT_LINE('Second loop i: ' || i);
> END LOOP;
> END;
> /
> ```

> [accordion] END; statements should be labeled
>
> Labels are useful to match the begin and end of each PACKAGE, PROCEDURE or FUNCTION, especially when the code is badly indented or too much nested.
>
> This rule raised an issue when the END statement of a PACKAGE, PROCEDURE or FUNCTION is having no label matching the name of the corresponding "begin" statement.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE OR REPLACE PACKAGE BODY cust_sal AS  
>
> PROCEDURE find_sal(c_id customers.id%TYPE) IS 
> c_sal customers.salary%TYPE; 
> BEGIN 
>   SELECT salary INTO c_sal 
>   FROM customers 
>   WHERE id = c_id; 
>   dbms_output.put_line('Salary: '|| c_sal); 
> END; -- Noncompliant; not a PROCEDURE
> END; -- Noncompliant; not a PACKAGE
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> CREATE OR REPLACE PACKAGE BODY cust_sal AS  
>
> PROCEDURE find_sal(c_id customers.id%TYPE) IS 
> c_sal customers.salary%TYPE; 
> BEGIN 
>   SELECT salary INTO c_sal 
>   FROM customers 
>   WHERE id = c_id; 
>   dbms_output.put_line('Salary: '|| c_sal); 
> END find_sal; -- Compliant; it's matching the name of the PROCEDURE
> END cust_sal; -- Compliant: it's matching the name of the PACKAGE
> /
> ```

> [accordion] UNION should be used with caution
>
> \`UNION is a convenient syntax to combine the results of two or more SQL statements because it helps you cut a complex problem into multiple simple SQL statements. But when it comes to execution, using UNION is debatable.
>
> First, it may be possible to fuse two simple SQL statements into a bigger one that will run faster. Second, UNION is significantly less performant compared to UNION ALL because it removes duplicated entries and runS an internal DISTINCT to achieve this.
>
> UNION ALL does not remove duplicates and returns all the results from the queries. It performs faster in most cases compared to UNION. Nevertheless, the quantity of data returned by UNION ALL can be significantly larger than with UNION. On a slow network, the performance gain of using UNION ALL instead of UNION can be negated by the time lost in the larger data transfer.
>
> This rule raises an issue on each UNION. It’s up to the developer to challenge its use and see if there is a better way to rewrite without UNION\`.
>
> ```plsql Bad theme={"theme":"css-variables"}
> -- case #1
> SELECT EMAIL FROM EMPLOYEES WHERE COUNTRY = 'FR'
> UNION                           -- Noncompliant
> SELECT EMAIL FROM EMPLOYEES WHERE COUNTRY = 'CH'
>
> -- case #2
> -- if you care about not having duplicated entries, then UNION is the good choice
> SELECT EMAIL FROM EMPLOYEES 
> UNION                           -- Noncompliant
> SELECT EMAIL FROM CUSTOMERS
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> -- case #1
> SELECT EMAIL FROM EMPLOYEES WHERE COUNTRY = 'FR' OR COUNTRY = 'CH'
>
> -- case #2
> -- if you don't care about duplicated entries in the results of this UNION, then UNION ALL should be preferred
> SELECT EMAIL FROM EMPLOYEES 
> UNION ALL
> SELECT EMAIL FROM CUSTOMERS
> ```

> [accordion] IF statement conditions should not evaluate unconditionally to TRUE or to FALSE
>
> `IF statements with conditions that are always false have the effect of making blocks of code non-functional. This can be useful during debugging, but should not be checked in. IF statements with conditions that are always true are completely redundant, and make the code less readable. In either case, unconditional IF` statements should be removed.
>
> ```plsql Bad theme={"theme":"css-variables"}
> IF TRUE THEN
> do_something;
> END IF;
>
> IF FALSE THEN
> do_something_else;
> END IF;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> do_something;
> ```

> [accordion] GOTO should not be used to jump backwards
>
> Jumping back to a previous statement using `GOTO` is a way to reimplement loops, which PL/SQL already provides in much more readable forms.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> result PLS_INTEGER := 0;
> counter PLS_INTEGER := 1;
> BEGIN
> <<loop>>
> result := result + counter;
> counter := counter + 1;
>
> IF counter <= 9 THEN
> GOTO loop;                    -- Noncompliant
> END IF;
>
> DBMS_OUTPUT.PUT_LINE('Sum from 1 to 9 is ' || result); -- Displays 1 + 2 + ... + 8 + 9 = 45
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> result PLS_INTEGER := 0;
> BEGIN
> FOR counter IN 1 .. 9 LOOP
> result := result + counter;
> END LOOP;
>
> DBMS_OUTPUT.PUT_LINE('Sum from 1 to 9 is ' || result); -- Displays 1 + 2 + ... + 8 + 9 = 45
> END;
> /
> ```

> [accordion] RAISE\_APPLICATION\_ERROR should only be used with error codes from -20,000 to -20,999
>
> `RAISE_APPLICATION_ERROR may only be called with an error code from -20,000 to -20,999, which is the range reserved for application errors. When called with another value, Oracle raises the exception: ORA-21000: error number argument to raise_application_error of 0 is out of range.`
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> RAISE_APPLICATION_ERROR(0, 'This is an application error'); -- Non-Compliant - raises ORA-21000
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> BEGIN
> RAISE_APPLICATION_ERROR(-20000, 'This is an application error'); -- Compliant
> END;
> /
> ```

> [accordion] MLSLABEL should not be used
>
> The deprecated MLSLABEL datatype is still supported only for backwards compatibility with Trusted Oracle, and since Oracle8, the only valid value it can hold is NULL. Thus, the usage of this type should be progressively removed.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> foo MLSLABEL; -- Noncompliant
> BEGIN
> NULL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] VARCHAR2 and NVARCHAR2 should be used
>
> For fixed-length values, a \`CHAR field occupies the same amount of disk space as a VARCHAR2 field, but for variable-length values CHAR fields use more storage space and make searching more difficult by right-padding values with whitespaces. Therefore VARCHAR2 fields are preferred. Similarly, NCHAR should be replaced by NVARCHAR2.
>
> Note that for 1-character fields, CHAR is naturally equivalent to VARCHAR2\`, but the latter is still preferred for consistency.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> var1 CHAR; -- Noncompliant
>
> var2 CHAR(42); -- Noncompliant
>
> var3 NCHAR; -- Noncompliant
>
> var4 NCHAR(42); -- Noncompliant
> BEGIN
> NULL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> var1 VARCHAR2(42); 
>
> var2 VARCHAR2(42);
>
> var3 NVARCHAR2(42); 
>
> var4 NVARCHAR2(42);
> BEGIN
> NULL;
> END;
> /
> ```

> [accordion] Labels should not be reused in inner scopes
>
> Using the same name for multiple purposes reduces the understandability of the code and might eventually lead to bugs.
>
> This rule verifies that no label is reused in an inner scope.
>
> ```plsql Bad theme={"theme":"css-variables"}
> <<foo>>
> DECLARE
> a CONSTANT PLS_INTEGER := 0;
> BEGIN
> <<foo>>                                  -- Noncompliant
> DECLARE
> b CONSTANT PLS_INTEGER := 42;
> BEGIN
> DBMS_OUTPUT.PUT_LINE('x = ' || foo.b); -- Confusing
> END;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> <<foo>>
> DECLARE
> a CONSTANT PLS_INTEGER := 0;
> BEGIN
> <<bar>>
> DECLARE
> b CONSTANT PLS_INTEGER := 42;
> BEGIN
> DBMS_OUTPUT.PUT_LINE('x = ' || bar.b);
> END;
> END;
> /
> ```

> [accordion] CROSS JOIN queries should not be used
>
> A `CROSS JOIN` query will return all records where each row from the first table is combined with each row from the second table. This means that such a query returns the Cartesian product of the sets of rows from the joined tables, which is why it is also know as "Cartesian product query".
>
> Such a query can return a huge amount of data, and therefore should be used only with great caution and only when really needed.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> -- Standard ANSI syntax
> SELECT *
> INTO employeeArray
> FROM employee CROSS JOIN department; -- Noncompliant; explicit cross join
> END;
> /
>
> BEGIN
> -- Old syntax
> SELECT *
> INTO employeeArray
> FROM employee, department; -- Noncompliant; also a cross join
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] RESULT\_CACHE should not be used
>
> Because `RESULT_CACHE`-enabled functions increase memory consumption, one should double-check that the gain in performances is significant, and avoid over-using this feature in general.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE FUNCTION myFastFunction RETURN PLS_INTEGER RESULT_CACHE AS -- Noncompliant
> BEGIN
> RETURN 42;
> END;
> /
>
> DROP FUNCTION myFastFunction;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] FOR loop end conditions should not be hard-coded
>
> Hard-coding bounds in FOR loops is a bad practice, just as magic numbers in general are. Often, those magic bounds can be replaced by dynamic values. If that is not possible, replacing the literal number with a constant is still better.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> TYPE myCollectionType IS VARRAY(3) OF VARCHAR2(42);
> myCollection myCollectionType := myCollectionType('David', 'John', 'Richard');
>
> BEGIN
>
> FOR i IN 2 .. 3 -- Noncompliant; magic numbers used for the loop bounds
> LOOP
> DBMS_OUTPUT.PUT_LINE('name = ' || myCollection(i));
> END LOOP;
>
> FOR i IN 2 .. myCollection.LAST -- Noncompliant, better but still magic
> LOOP
> DBMS_OUTPUT.PUT_LINE('name = ' || myCollection(i));
> END LOOP;
>
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> TYPE myCollectionType IS VARRAY(3) OF VARCHAR2(42);
> myCollection myCollectionType := myCollectionType('David', 'John', 'Richard');
>
> BEGIN
> FOR i IN myCollection.FIRST .. myCollection.LAST
> LOOP
> DBMS_OUTPUT.PUT_LINE('name = ' || myCollection(i));
> END LOOP;
> END;
> /
> ```

> [accordion] Large item lists should not be used with IN clauses
>
> Oracle supports at most 1000 items in a SQL query’s `IN clause. When more items are given, the exception ORA-01795 maximum number of expressions in a list is 1000 is raised. Thus, IN` clauses are not as scalable as joins.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> SELECT *
> INTO result
> FROM my_table
> WHERE col1 IN (1, 2, 3, ..., 1001);       -- Noncompliant - raises ORA-01795
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> BEGIN
> SELECT my_table.*
> INTO result
> FROM my_table
> JOIN new_in_table
> WHERE my_table.col1 = new_in_table.value; -- Compliant
> END;
> /
> ```

> [accordion] FORALL should be used
>
> The performance of DML queries in loops can be improved by placing them in a `FORALL` statement. This way, queries will be sent in bulk, minimizing the number of context switches between PL/SQL and SQL.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> CREATE TABLE largeTable(
> foo VARCHAR2(42)
> );
>
> BEGIN
> FOR i IN 1 .. 100000 LOOP
> INSERT INTO largeTable VALUES('bar' || i); -- Non-compliant
> END LOOP;
> END;
> /
>
> SET TIMING ON
> DECLARE
> TYPE largeTableRowArrayType IS TABLE OF largeTable%ROWTYPE;
> largeTableRowArray largeTableRowArrayType;
> BEGIN
> SELECT * BULK COLLECT INTO largeTableRowArray FROM largeTable;
>
> EXECUTE IMMEDIATE 'TRUNCATE TABLE largeTable';
> FOR i IN largeTableRowArray.FIRST .. largeTableRowArray.LAST LOOP
> INSERT INTO largeTable (foo) VALUES (largeTableRowArray(i).foo); -- Non-compliant
> END LOOP;
> END;
> /
> SET TIMING OFF
>
> DROP TABLE largeTable;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> CREATE TABLE largeTable(
> foo VARCHAR2(42)
> );
>
> BEGIN
> FOR i IN 1 .. 100000 LOOP
> INSERT INTO largeTable VALUES('bar' || i); -- Non-compliant
> END LOOP;
> END;
> /
>
> SET TIMING ON
> DECLARE
> TYPE largeTableRowArrayType IS TABLE OF largeTable%ROWTYPE;
> largeTableRowArray largeTableRowArrayType;
> BEGIN
> SELECT * BULK COLLECT INTO largeTableRowArray FROM largeTable;
>
> EXECUTE IMMEDIATE 'TRUNCATE TABLE largeTable';
> FORALL i IN largeTableRowArray.FIRST .. largeTableRowArray.LAST
> INSERT INTO largeTable (foo) VALUES (largeTableRowArray(i).foo); -- Compliant
>
> INSERT INTO largeTable (foo) VALUES ('baz'); -- Compliant, not in a loop
> END;
> /
> SET TIMING OFF
>
> DROP TABLE largeTable;
> ```

> [accordion] Unused cursor parameters should be removed
>
> Unused cursor parameters are misleading. Whatever the values passed to such parameters, the behavior will be the same.
>
> ```plsql Bad theme={"theme":"css-variables"}
> cursor c_list_emp(pp_country varchar2, pp_status varchar2)  is -- Noncompliant pp_status is not used
> select e.employee_code,
>       p.first_name,
>       p.last_name,
>       e.country
> from persons       p,
> join employee_list e on e.person_id = p.person_id
> where e.country = pp_country;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> cursor c_list_emp(pp_country varchar2, pp_status varchar2)  is
> select e.employee_code,
>       p.first_name,
>       p.last_name,
>       e.country
> from persons       p,
> join employee_list e on e.person_id = p.person_id
> where e.country     = pp_country
>  and e.status_code = pp_status; -- use the parameter
> ```

> [accordion] PACKAGE BODY initialization sections should not contain RETURN statements
>
> In a CREATE PACKAGE BODY, the purpose of the initialization section is to set the initial values of the package’s global variables. It is therefore surprising to find a RETURN statement there, as all its following statements will be unreachable.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> CREATE OR REPLACE PACKAGE foo AS
> FUNCTION getBar RETURN PLS_INTEGER;
> bar PLS_INTEGER;
> END;
> /
>
> CREATE OR REPLACE PACKAGE BODY foo AS
> FUNCTION getBar RETURN PLS_INTEGER AS
> BEGIN
> RETURN bar; -- Compliant
> END;
> BEGIN
> bar := 42;
> DBMS_OUTPUT.PUT_LINE('package loaded');
> RETURN; -- Noncompliant
> DBMS_OUTPUT.PUT_LINE('this is unreachable code');
> END;
> /
>
> DROP PACKAGE BODY foo;
>
> DROP PACKAGE foo;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] Collections should not be iterated in FOR loops
>
> The \`FOR loop at first seems like a convenient way of iterating over the elements of a collection, but doing so will raise a VALUE\_ERROR exception if the collection is empty. Looping instead from 1 to COUNT doesn’t work either if the collection is sparse; that leads to a ORA-01403: no data found error.
>
> Instead, a WHILE\` loop should be used.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> TYPE fooType IS TABLE OF VARCHAR2(42);
> foo fooType := new fooType('Strawberry', 'Apple', 'Banana');
> BEGIN
> foo.DELETE(2);                                -- The collection is now sparse
>
> FOR i IN 1 .. foo.COUNT                       -- Noncompliant - leads to ORA-01403: no data found
> LOOP
> DBMS_OUTPUT.PUT_LINE(i || ' = ' || foo(i));
> END LOOP;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> TYPE fooType IS TABLE OF VARCHAR2(42);
> foo fooType := new fooType('Strawberry', 'Apple', 'Banana');
> i PLS_INTEGER;
> BEGIN
> foo.DELETE(2);                                -- The collection is now sparse
>
> i := foo.FIRST;
>
> WHILE (i IS NOT NULL)                         -- Compliant - works as expected
> LOOP
> DBMS_OUTPUT.PUT_LINE(i || ' = ' || foo(i));
> i := foo.NEXT(i);
> END LOOP;
> END;
> /
> ```

> [accordion] CASE statements should end with ELSE clauses
>
> The requirement for a final `ELSE clause is defensive programming. The CASE` statement should always provide a value.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CASE grade -- Noncompliant, can raise a CASE_NOT_FOUND exception.
> WHEN 'A' THEN DBMS_OUTPUT.PUT_LINE('Excellent');
> WHEN 'B' THEN DBMS_OUTPUT.PUT_LINE('Very Good');
> END CASE;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> CASE grade
> WHEN 'A' THEN DBMS_OUTPUT.PUT_LINE('Excellent');
> WHEN 'B' THEN DBMS_OUTPUT.PUT_LINE('Very Good');
> ELSE DBMS_OUTPUT.PUT_LINE('No such grade');
> END CASE;
> ```

> [accordion] Quoted identifiers should not be used
>
> Quoted identifiers are confusing to many programmers, as they look similar to string literals. Moreover, for maximum portability, identifiers should be self-descriptive and should not contain accents. Quoted identifiers can contain any character, which can be confusing.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> "x + y" PLS_INTEGER := 0; -- Noncompliant, quoted identifiers are confusing
> x PLS_INTEGER := 40;
> y PLS_INTEGER := 2;
> "hello" VARCHAR2(42) := 'world';  -- Noncompliant
>
> BEGIN
> DBMS_OUTPUT.PUT_LINE("x + y"); -- Noncompliant, displays 0
> DBMS_OUTPUT.PUT_LINE("hello"); -- Noncompliant, confusing, displays "world" and not "hello"
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> my_int PLS_INTEGER := 0;
> x PLS_INTEGER := 40;
> y PLS_INTEGER := 2;
> greeting VARCHAR2(42) := 'hello';
> BEGIN
> DBMS_OUTPUT.PUT_LINE(my_int);
> DBMS_OUTPUT.PUT_LINE(x + y); -- Compliant, displays 42
>
> DBMS_OUTPUT.PUT_LINE(greeting);
> END;
> /
> ```

> [accordion] FORALL should be used with INDICES OF instead of IN
>
> Using `FORALL i IN x.first ... x.last or FORALL i IN 1 ... x.count might fail when indexed collections are sparse as Oracle tries to access non-existent element(s) of x. FORALL i IN INDICES OF x syntax will always work including sparse collections. Thus using FORALL i IN INDICES OF x` should be preferred as it makes code more robust and easier to review.
>
> ```plsql Bad theme={"theme":"css-variables"}
> FORALL i IN 1 .. l_tab.COUNT  -- Non-Compliant
> INSERT INTO forall_test VALUES l_tab(i);
>
> FORALL i IN l_tab.first .. l_tab.last  -- Non-Compliant
> INSERT INTO forall_test VALUES l_tab(i);
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> FORALL i IN INDICES OF l_tab
> INSERT INTO forall_test VALUES l_tab(i);
> ```

> [accordion] Boolean checks should not be inverted
>
> It is needlessly complex to invert the result of a boolean comparison. The opposite comparison should be made instead.
>
> ```plsql Bad theme={"theme":"css-variables"}
> IF NOT x <> y THEN   -- Noncompliant
> -- ...
> END IF;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> IF x = y THEN
> -- ...
> END IF;
> ```

> [accordion] Lines should not end with trailing whitespaces
>
> Trailing whitespaces bring no information, they may generate noise when comparing different versions of the same file, and they can create bugs when they appear after a \ marking a line continuation. They should be systematically removed.
>
> An automated code formatter allows to completely avoid this family of issues and should be used wherever possible.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> -- The following line has many trailing whitespaces
> foo VARCHAR2(42) := 'a     
> b';
> BEGIN
> -- Will misleadingly show 3, counting only the characters 'a', 'b', and the line terminator, but none of the trailing whitespaces
> DBMS_OUTPUT.PUT_LINE(LENGTH(foo));
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] Statements should be on separate lines
>
> Putting multiple statements on a single line lowers the code readability and makes debugging the code more complex.
>
> Unresolved directive in \<stdin> - include::\{noncompliant}\[]
>
> Write one statement per line to improve readability.
>
> Unresolved directive in \<stdin> - include::\{compliant}\[]
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> DBMS_OUTPUT.PUT_LINE('Hello '); DBMS_OUTPUT.PUT_LINE('World'); -- Noncompliant
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> BEGIN
> DBMS_OUTPUT.PUT_LINE('Hello ');
> DBMS_OUTPUT.PUT_LINE('World');
> END;
> /
> ```

> [accordion] SQL JOIN conditions should involve all joined tables
>
> When a SQL query is joining n tables (with n>=2), it is expected to have join conditions defined to determine on which columns these n tables should be joined. At minimum, for n joined tables, the SQL query should contain (n-1) join conditions involving all the joined table to avoid a full cartesian product between the rows of the n tables.
>
> Not doing so will imply that too many rows will be returned. If this is not the case and unless this has been done on purpose, the SQL query should be reviewed and missing conditions should be added or useless tables should be removed from the SQL query.
>
> This rule is raising no issue when the SQL query is involving `CROSS JOIN, NATURAL JOIN` statements.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SELECT c.id, c.name, o.id, o.item_id, o.item_quantity
> FROM ORDERS o, CUSTOMERS c; -- Noncompliant; no JOIN condition at all
>
> SELECT c.id, c.name, o.id, o.item_id, o.item_quantity
> FROM ORDERS o
> JOIN CUSTOMERS c ON o.customer_id = o.id; -- Noncompliant; no condition related to CUSTOMERS
>
> SELECT f.name, d.title, l.*
> FROM FOLDERS f, DOCUMENTS d, DOC_LINES l -- Noncompliant; missing at least one condition related to DOC_LINES
> WHERE f.id = d.folder_id;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SELECT c.id, c.name, o.id, o.item_id, o.item_quantity
> FROM ORDERS o, CUSTOMERS c
> WHERE o.customer_id = c.id; -- Compliant
>
> SELECT c.id, c.name, o.id, o.item_id, o.item_quantity
> FROM ORDERS o
> JOIN CUSTOMERS c ON o.customer_id = c.id; -- Compliant
>
> SELECT f.name, d.title, l.*
> FROM FOLDERS f, DOCUMENTS d, DOC_LINES l
> WHERE f.id = d.folder_id
> AND d.id = l.document_id; -- Compliant
> ```

> [accordion] Exception handlers should preserve the original exceptions
>
> When handling a caught exception, the original exception’s message and stack trace should be logged or passed forward.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> d VARCHAR2(1);
> BEGIN
> SELECT dummy INTO d FROM DUAL WHERE dummy = 'Y'; -- Will raise NO_DATA_FOUND
> DBMS_OUTPUT.PUT_LINE('d = ' || d);
> EXCEPTION
> WHEN NO_DATA_FOUND THEN -- Noncompliant, did we really want to mask this exception?
> NULL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> d VARCHAR2(1);
> BEGIN
> SELECT dummy INTO d FROM DUAL WHERE dummy = 'Y'; -- Will raise NO_DATA_FOUND
> DBMS_OUTPUT.PUT_LINE('d = ' || d);
> EXCEPTION
> WHEN NO_DATA_FOUND THEN
> DBMS_OUTPUT.PUT_LINE('Error: No data found');
> END;
> /
> ```

> [accordion] DDL statements should not be used
>
> Allowing an application to dynamically change the structure of a database at runtime is very dangerous because the application can become unstable under unexpected conditions. Best practices dictate that applications only manipulate data.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE TABLE my_table(
> my_column INTEGER
> );
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] Magic numbers should not be used
>
> Magic numbers make the code more complex to understand as it requires the reader to have knowledge about the global context to understand the number itself.
> Their usage may seem obvious when writing the code, but it may not be the case for another developer or later once the context faded away.
> -1, 0, and 1 are not considered magic numbers.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> FOR l_counter IN 1..5 -- Noncompliant, 5 is a magic number
> LOOP
> ...
> END LOOP;
> END;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> co_number_of_cycles CONSTANT NUMBER := 5;
> BEGIN
> FOR l_counter IN 1..co_number_of_cycles -- Compliant
> LOOP
> ...
> END LOOP;
> END;
> ```

> [accordion] Boolean literals should not be redundant
>
> A boolean literal can be represented in two different ways: \{true} or \{false}.
> They can be combined with logical operators (\{ops}) to produce logical expressions that represent truth values.
> However, comparing a boolean literal to a variable or expression that evaluates to a boolean value is unnecessary and can make the code harder to read and understand.
> The more complex a boolean expression is, the harder it will be for developers to understand its meaning and expected behavior, and it will favour the introduction of new bugs.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> foo BOOLEAN := TRUE;
> BEGIN
> IF foo = FALSE THEN                     -- Noncompliant
> DBMS_OUTPUT.PUT_LINE('foo = false!');
> ELSIF foo = TRUE THEN                   -- Noncompliant
> DBMS_OUTPUT.PUT_LINE('foo = true!');
> END IF;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> foo BOOLEAN := TRUE;
> BEGIN
> IF NOT foo THEN                         -- Compliant
> DBMS_OUTPUT.PUT_LINE('foo = false!');
> ELSIF foo THEN                          -- Compliant
> DBMS_OUTPUT.PUT_LINE('foo = true!');
> END IF;
> END;
> /
> ```

> [accordion] Exceptions should not be ignored
>
> When exceptions occur, it is usually a bad idea to simply ignore them. Instead, it is better to handle them properly, or at least to log them.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> d VARCHAR2(1);
> BEGIN
> SELECT dummy INTO d FROM DUAL WHERE dummy = 'Y'; -- Will raise NO_DATA_FOUND
> DBMS_OUTPUT.PUT_LINE('d = ' || d);
> EXCEPTION
> WHEN NO_DATA_FOUND THEN -- Noncompliant, did we really want to mask this exception?
> NULL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] SQL EXISTS subqueries should not be used
>
> SQL queries that use `EXISTS subqueries are inefficient because the subquery is re-run for every row in the outer query’s table. There are more efficient ways to write most queries, ways that do not use the EXISTS` condition.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SELECT e.name
> FROM employee e
> WHERE EXISTS (SELECT * FROM department d WHERE e.department_id = d.id AND d.name = 'Marketing');
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SELECT e.name
> FROM employee e INNER JOIN department d
> ON e.department_id = d.id AND d.name = 'Marketing';
> ```

> [accordion] Mergeable if statements should be combined
>
> Nested code - blocks of code inside blocks of code - is eventually necessary, but increases complexity. This is why keeping the code as flat as possible, by avoiding unnecessary nesting, is considered a good practice.
>
> Merging if statements when possible will decrease the nesting of the code and improve its readability.
>
> ```plsql Bad theme={"theme":"css-variables"}
> IF something THEN
> IF something_else THEN             -- Noncompliant
> -- ...
> END IF;
> END IF;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> IF something AND something_else THEN -- Compliant
> -- ...
> END IF;
> ```

> [accordion] Track lack of copyright and license headers
>
> Each source file should start with a header stating file ownership and the license which must be used to distribute the application.
>
> This rule must be fed with the header text that is expected at the beginning of every file.
>
> ```plsql Bad theme={"theme":"css-variables"}
> --
> -- SonarQube, open source software quality management tool.
> -- Copyright (C) 2008-2018 SonarSource
> -- mailto:contact AT sonarsource DOT com
> --
> -- SonarQube is free software; you can redistribute it and/or
> -- modify it under the terms of the GNU Lesser General Public
> -- License as published by the Free Software Foundation; either
> -- version 3 of the License, or (at your option) any later version.
> --
> -- SonarQube is distributed in the hope that it will be useful,
> -- but WITHOUT ANY WARRANTY; without even the implied warranty of
> -- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> -- Lesser General Public License for more details.
> --
> -- You should have received a copy of the GNU Lesser General Public License
> -- along with this program; if not, write to the Free Software Foundation,
> -- Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
> --
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] Redundant pairs of parentheses should be removed
>
> The use of parentheses, even those not required to enforce a desired order of operations, can clarify the intent behind a piece of code. However, redundant pairs of parentheses could be misleading and should be removed.
>
> ```plsql Bad theme={"theme":"css-variables"}
> x := (y / 2 + 1); -- Compliant even if the parentheses are ignored
> IF (x > 0) AND ((x+y > 0)) THEN -- Noncompliant
> -- ...
> END IF;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> x := (y / 2 + 1);
> IF (x > 0) AND (x+y > 0) THEN
> -- ...
> END IF;
> ```

> [accordion] DELETE and UPDATE statements should contain WHERE clauses
>
> `UPDATE and DELETE statements should contain WHERE` clauses to keep the modification of records under control. Otherwise unexpected data loss could result.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> maxAge PLS_INTEGER := 60;
> BEGIN
> UPDATE employee SET status = 'retired'; -- Noncompliant - the WHERE was forgotten
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> maxAge PLS_INTEGER := 60;
> BEGIN
> UPDATE employee SET status = 'retired' WHERE age > maxAge;
> END;
> /
> ```

> [accordion] Unused procedure and function parameters should be removed
>
> A typical code smell known as unused function parameters refers to parameters declared in a function but not used anywhere within the function’s body.
> While this might seem harmless at first glance, it can lead to confusion and potential errors in your code.
> Disregarding the values passed to such parameters, the function’s behavior will be the same, but the programmer’s intention won’t be clearly expressed anymore.
> Therefore, removing function parameters that are not being utilized is considered best practice.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE PROCEDURE say_hello(name VARCHAR2) AS -- Noncompliant; name is not used
> BEGIN
> DBMS_OUTPUT.PUT_LINE('Hello World');
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> CREATE PROCEDURE say_hello(name VARCHAR2) AS -- Compliant
> BEGIN
> DBMS_OUTPUT.PUT_LINE('Hello ' || name);
> END;
> /
> ```

> [accordion] Package names should comply with a naming convention
>
> Shared naming conventions improve readability and allow teams to collaborate efficiently.
> This rule checks that all package names match a provided regular expression.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE OR REPLACE PACKAGE invalid_package_ AS
> PROCEDURE display_message;
> END invalid_package_;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> CREATE OR REPLACE PACKAGE valid_package AS
> PROCEDURE display_message;
> END valid_package;
> ```

> [accordion] Variables and columns should not be self-assigned
>
> There is no reason to re-assign a variable to itself. Either this statement is redundant and should be removed, or the re-assignment is a mistake and some other value or variable was intended for the assignment instead.
>
> ```plsql Bad theme={"theme":"css-variables"}
> UPDATE person
> SET name = name;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> UPDATE person
> SET name = UPPER(name);
> ```

> [accordion] Dynamically executing code is security-sensitive
>
> Executing code dynamically is security-sensitive. It has led in the past to the following vulnerabilities:
>
> <ul>
>   <li>
>     [CVE-2017-9807](http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-9807)
>   </li>
>
>   <li>
>     [CVE-2017-9802](http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-9802)
>   </li>
> </ul>
>
> Some APIs enable the execution of dynamic code by providing it as strings at runtime. These APIs might be useful in some very specific meta-programming use-cases. However most of the time their use is frowned upon because they also increase the risk of maliciously [Injected Code](https://owasp.org/www-community/attacks/Code_Injection). Such attacks can either run on the server or in the client (example: XSS attack) and have a huge impact on an application’s security.
>
> This rule marks for review each occurrence of such dynamic code execution. This rule does not detect code injections. It only highlights the use of APIs which should be used sparingly and very carefully.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE OR REPLACE PROCEDURE ckpwd_bind (p_user IN VARCHAR2, p_pass IN VARCHAR2) 
> IS
> v_query  VARCHAR2(100);
> v_output NUMBER;
> BEGIN
> v_query := 
> q'{SELECT COUNT(*) FROM user_pwd WHERE username = :1 AND password = :2}';
> EXECUTE IMMEDIATE v_query 
> INTO v_output
> USING p_user, p_pass;
> END;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] String literals should not be duplicated
>
> Duplicated string literals make the process of refactoring complex and error-prone, as any change would need to be propagated on all occurrences.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> prepare('action1');
> execute('action1');
> release('action1');
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> co_action CONSTANT VARCHAR2(7) := 'action1';
> BEGIN
> prepare(co_action);
> execute(co_action);
> release(co_action);
> END;
> /
> ```

> [accordion] Columns to be read with a SELECT statement should be clearly defined
>
> `SELECT *` should be avoided because it releases control of the returned columns and could therefore lead to errors and potentially to performance issues.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> myvar CHAR;
> BEGIN
> SELECT * INTO myvar FROM DUAL; -- Noncompliant
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> myvar CHAR;
> BEGIN
> SELECT dummy INTO myvar FROM DUAL;
> END;
> /
> ```

> [accordion] Neither DES (Data Encryption Standard) nor DESede (3DES) should be used
>
> According to the US National Institute of Standards and Technology (NIST), the Data Encryption Standard (DES) is no longer considered secure:
>
> > Adopted in 1977 for federal agencies to use in protecting sensitive, unclassified information, the DES is being withdrawn because it no longer provides the security that is needed to protect federal government information.
> >
> > Federal agencies are encouraged to use the Advanced Encryption Standard, a faster and stronger algorithm approved as FIPS 197 in 2001.
>
> For similar reasons, RC2 should also be avoided.
>
> ```plsql Bad theme={"theme":"css-variables"}
> PLS_INTEGER := DBMS_CRYPTO.ENCRYPT_DES
>                        + DBMS_CRYPTO.CHAIN_CBC
>                        + DBMS_CRYPTO.PAD_PKCS5;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> PLS_INTEGER := DBMS_CRYPTO.ENCRYPT_AES256
>                        + DBMS_CRYPTO.CHAIN_CBC
>                        + DBMS_CRYPTO.PAD_PKCS5;
> ```

> [accordion] Output parameters should be assigned
>
> Marking a parameter for output means that callers will expect its value to be updated with a result from the execution of the procedure. Failing to update the parameter before the procedure returns is surely an error.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE OR REPLACE PROCEDURE greet(
> name     IN  VARCHAR2,
> greeting OUT VARCHAR2) -- Noncompliant
> AS
> message VARCHAR2(45);
> BEGIN
> SELECT 'Hello ' || RTRIM(name) INTO message FROM DUAL;
> END;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> CREATE OR REPLACE PROCEDURE greet(
> name     IN  VARCHAR2,
> greeting OUT VARCHAR2)
> AS
> BEGIN
> SELECT 'Hello ' || RTRIM(name) INTO greeting FROM DUAL;
> END;
> ```

> [accordion] SHA-1 and Message-Digest hash algorithms should not be used in secure contexts
>
> The MD5 algorithm and its successor, SHA-1, are no longer considered secure, because it is too easy to create hash collisions with them. That is, it takes too little computational effort to come up with a different input that produces the same MD5 or SHA-1 hash, and using the new, same-hash value gives an attacker the same access as if he had the originally-hashed value. This applies as well to the other Message-Digest algorithms: MD2, MD4, MD6, HAVAL-128, HMAC-MD5, DSA (which uses SHA-1), RIPEMD, RIPEMD-128, RIPEMD-160, HMACRIPEMD160.
>
> Consider using safer alternatives, such as SHA-256, SHA-512 or SHA-3.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DBMS_CRYPTO.Hash(str, HASH_MD4);
>
> DBMS_CRYPTO.Hash(str, HASH_MD5);
>
> DBMS_CRYPTO.Hash(str, HASH_SH1);
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> ```

> [accordion] Comments should not be located at the end of lines of code
>
> This rule verifies that single-line comments are not located at the ends of lines of code. The main idea behind this rule is that in order to be really readable, trailing comments would have to be properly written and formatted (correct alignment, no interference with the visual structure of the code, not too long to be visible) but most often, automatic code formatters would not handle this correctly: the code would end up less readable. Comments are far better placed on the previous empty line of code, where they will always be visible and properly formatted.
>
> ```plsql Bad theme={"theme":"css-variables"}
> a := b + c; -- This is a trailing comment that can be very very long
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> -- This very long comment is better placed before the line of code
> a := b + c;
> ```

> [accordion] Function and procedure names should comply with a naming convention
>
> Shared coding conventions allow teams to collaborate efficiently. This rule checks that all function names match a provided regular expression.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE FUNCTION my_function_ RETURN PLS_INTEGER AS -- Noncompliant
> BEGIN
> RETURN 42;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> CREATE FUNCTION my_function RETURN PLS_INTEGER AS
> BEGIN
> RETURN 42;
> END;
> /
> ```

> [accordion] Variables should not be shadowed
>
> Overriding a variable declared in an outer scope can strongly impact the readability, and therefore the maintainability, of a piece of code. Further, it could lead maintainers to introduce bugs because they think they’re using one variable but are really using another.
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> foo VARCHAR2(42) := 'foo';
> BEGIN
> DECLARE
> foo VARCHAR2(42) := 'bar'; -- Noncompliant - this variable hides the one above and should be renamed
> BEGIN
> DBMS_OUTPUT.PUT_LINE(foo); -- Displays "bar", which is confusing
> END;
>
> DBMS_OUTPUT.PUT_LINE(foo); -- Displays "foo"
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> foo VARCHAR2(42) := 'foo';
> BEGIN
> DECLARE
> bar VARCHAR2(42) := 'bar'; -- Compliant
> BEGIN
> DBMS_OUTPUT.PUT_LINE(bar); -- Displays "bar"
> END;
>
> DBMS_OUTPUT.PUT_LINE(foo); -- Displays "foo"
> END;
> /
> ```

> [accordion] A primary key should be specified during table creation
>
> Tables without primary keys are largely unusable in a relational database because they cannot be joined to. A primary key should be specified at table creation to guarantee that all its records have primary key values.
>
> ```plsql Bad theme={"theme":"css-variables"}
> CREATE TABLE employee
> (
> employee_id INTEGER NOT NULL,
> first_name VARCHAR2(42) NOT NULL,
> last_name VARCHAR2(42) NOT NULL  
> );
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> CREATE TABLE employee
> (
> employee_id INTEGER PRIMARY KEY,
> first_name VARCHAR2(42) NOT NULL,
> last_name VARCHAR2(42) NOT NULL  
> );
> ```

> [accordion] Return of boolean expressions should not be wrapped into an if-then-else statement
>
> Return of boolean literal statements wrapped into `if-then-else` ones should be simplified.
>
> ```plsql Bad theme={"theme":"css-variables"}
> IF expression THEN
> RETURN TRUE;
> ELSE
> RETURN FALSE;
> END IF;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> RETURN expression;
> ```

> [accordion] Column names should be used in a SQL ORDER BY clause
>
> Even though the `ORDER BY` clause supports using column numbers, doing so makes the code difficult to read and maintain. Therefore the use of column names is preferred.
>
> ```plsql Bad theme={"theme":"css-variables"}
> BEGIN
> SELECT col2, col3
> BULK COLLECT INTO result
> FROM my_table
> ORDER BY
> 1 ASC;           -- Noncompliant - if col1 is added to the selected fields, this may break
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> BEGIN
> SELECT col2, col3
> BULK COLLECT INTO result
> FROM my_table
> ORDER BY
> col2 ASC;  
> END;
> /
> ```

> [accordion] Unused local variables should be removed
>
> An unused local variable is a variable that has been declared but is not used anywhere in the block of code where it is defined. It is dead code, contributing to unnecessary complexity and leading to confusion when reading the code. Therefore, it should be removed from your code to maintain clarity and efficiency.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> seconds INTEGER := 0; -- Noncompliant - seconds is unused
> hours INTEGER := 2;
> BEGIN
> minutes := hours * 60;
> DBMS_OUTPUT.PUT_LINE('Number of minutes: ' || minutes);
> END;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> hours INTEGER := 2;
> BEGIN
> minutes := hours * 60;
> DBMS_OUTPUT.PUT_LINE('Number of minutes: ' || minutes);
> END;
> ```

> [accordion] Unused assignments should be removed
>
> Dead stores refer to assignments made to local variables that are subsequently never used or immediately overwritten. Such assignments are unnecessary and don’t contribute to the functionality or clarity of the code. They may even negatively impact performance. Removing them enhances code cleanliness and readability.
> Even if the unnecessary operations do not do any harm in terms of the program’s correctness, they are - at best - a waste of computing resources.
>
> ```plsql Bad theme={"theme":"css-variables"}
> declare
> my_user VARCHAR2(30);
> my_date VARCHAR2(30);
> begin
> my_user := user();
> my_date := sysdate(); -- Noncompliant, the value of my_date is never read
> dbms_output.put_line('User:' || my_user || ', date: ' || my_user); 
> end;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> declare
> my_user VARCHAR2(30);
> my_date VARCHAR2(30);
> begin
> my_user := user();
> my_date := sysdate();
> dbms_output.put_line('User:' || my_user || ', date: ' || my_date);
> end;
> ```

> [accordion] Variables should comply with a naming convention
>
> A naming convention in software development is a set of guidelines for naming code elements like variables, functions, and classes.
> \{identifier\_capital\_plural} hold the meaning of the written code. Their names should be meaningful and follow a consistent and easily recognizable pattern.
> Adhering to a consistent naming convention helps to make the code more readable and understandable, which makes it easier to maintain and debug.
> It also ensures consistency in the code, especially when multiple developers are working on the same project.
>
> This rule checks that \{identifier} names match a provided regular expression.
>
> ```plsql Bad theme={"theme":"css-variables"}
> DECLARE
> badVariable_ PLS_INTEGER; -- Non-Compliant
> BEGIN
> NULL;
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> DECLARE
> goodVariable PLS_INTEGER; -- Compliant
> BEGIN
> NULL;
> END;
> /
> ```

> [accordion] Variables should not be shadowed
>
> Variables should not be shadowed
>
> ```plsql Bad theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> foo VARCHAR2(42) := 'foo';
> BEGIN
> DECLARE
> foo VARCHAR2(42) := 'bar'; -- Noncompliant - this variable hides the one above and should be renamed
> BEGIN
> DBMS_OUTPUT.PUT_LINE(foo); -- Displays "bar", which is confusing
> END;
>
> DBMS_OUTPUT.PUT_LINE(foo); -- Displays "foo"
> END;
> /
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> SET SERVEROUTPUT ON
>
> DECLARE
> foo VARCHAR2(42) := 'foo';
> BEGIN
> DECLARE
> bar VARCHAR2(42) := 'bar'; -- Compliant
> BEGIN
> DBMS_OUTPUT.PUT_LINE(bar); -- Displays "bar"
> END;
>
> DBMS_OUTPUT.PUT_LINE(foo); -- Displays "foo"
> END;
> /
> ```

> [accordion] Two branches in a conditional structure should not have exactly the same implementation
>
> Having two branches in an IF/ELSIF chain with the same implementation is at best duplicate code, and at worst a coding error.
>
> ```plsql Bad theme={"theme":"css-variables"}
> IF param = 1 THEN
> sort_order := 0;
> column := 'LastName';
> ELSIF param = 2 THEN
> sort_order := 0;
> column := 'LastName'; -- Noncompliant
> ELSE
> sort_order := 1;
> column := 'FirstName';
> END IF;
> ```
>
> ```plsql Fix theme={"theme":"css-variables"}
> IF param = 1 OR param = 2 THEN
> sort_order := 0;
> column := 'LastName';
> ELSE
> sort_order := 1;
> column := 'FirstName';
> END IF;
> ```


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