WHILE statement

The WHILE statement repeats the execution of a statement while a specified condition is true.

Syntax

>>-+--------+--WHILE--search-condition--DO---------------------->
   '-label:-'
 
   .-----------------------------.
   V                             |
>----SQL-procedure-statement-- ;-+--END WHILE--+-------+-------><
                                               '-label-'
 

Description

label

Specifies the label for the WHILE statement. If the ending label is specified, it must be the same as the beginning label. The label name cannot be the same as another label within the same scope. For more information, see Labels.

search-condition

Specifies a condition that is evaluated before each execution of the WHILE loop. If the condition is true, the SQL-procedure-statements in the WHILE loop are executed.

SQL-procedure-statement

Specifies an SQL statement or statements to execute within the WHILE loop.

Example

This example uses a WHILE statement to iterate through FETCH and SET statements. While the value of SQL variable v_counter is less than half of number of employees in the department identified by the IN parameter deptNumber, the WHILE statement continues to perform the FETCH and SET statements. When the condition is no longer true, the flow of control leaves the WHILE statement and closes the cursor.

CREATE PROCEDURE dept_median
   (IN deptNumber SMALLINT,
    OUT medianSalary DECIMAL(7,2))
    LANGUAGE SQL
    BEGIN
       DECLARE v_numRecords INTEGER DEFAULT 1;
       DECLARE v_counter INTEGER DEFAULT 0;
       DECLARE c1 CURSOR FOR
          SELECT salary
          FROM staff
          WHERE dept = deptNumber
          ORDER BY salary;
       DECLARE EXIT HANDLER FOR NOT FOUND
          SET medianSalary = 6666;
       SET medianSalary = 0;
       SELECT COUNT(*) INTO v_numRecords
          FROM staff
          WHERE dept = deptNumber;
       OPEN c1;
       WHILE v_counter < (v_numRecords/2 + 1) DO
          FETCH c1 INTO medianSalary;
          SET v_counter = v_counter +1;
       END WHILE;
       CLOSE c1;
    END