MySQL Tutorial/Procedure Function/While

IF statement in a While loop

mysql>
mysql> delimiter $$
mysql>
mysql> CREATE PROCEDURE myProc()
    -> BEGIN
    ->
    ->     DECLARE i int;
    ->     SET i=1;
    ->     loop1: WHILE i<=10 DO
    ->          IF MOD(i,2)<>0 THEN /*Even number - try again*/
    ->             SELECT CONCAT(i," is an odd number");
    ->          END IF;
    ->          SET i=i+1;
    ->     END WHILE loop1;
    -> END$$
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> delimiter ;
mysql> call myProc();
+-------------------------------+
| CONCAT(i," is an odd number") |
+-------------------------------+
| 1 is an odd number            |
+-------------------------------+
1 row in set (0.02 sec)
+-------------------------------+
| CONCAT(i," is an odd number") |
+-------------------------------+
| 3 is an odd number            |
+-------------------------------+
1 row in set (0.02 sec)
+-------------------------------+
| CONCAT(i," is an odd number") |
+-------------------------------+
| 5 is an odd number            |
+-------------------------------+
1 row in set (0.02 sec)
+-------------------------------+
| CONCAT(i," is an odd number") |
+-------------------------------+
| 7 is an odd number            |
+-------------------------------+
1 row in set (0.02 sec)
+-------------------------------+
| CONCAT(i," is an odd number") |
+-------------------------------+
| 9 is an odd number            |
+-------------------------------+
1 row in set (0.02 sec)
Query OK, 0 rows affected (0.38 sec)
mysql> drop procedure myProc;
Query OK, 0 rows affected (0.00 sec)
mysql>

While loop

mysql>
mysql>
mysql> delimiter //
mysql> create procedure test_while (IN in_count INT)
    -> BEGIN
    ->     declare count INT default 0;
    ->
    ->     while count < 10 do
    ->         set count = count + 1;
    ->     end while;
    ->
    ->     select count;
    -> END
    -> //
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> delimiter ;
mysql>
mysql> call test_while(10);
+-------+
| count |
+-------+
|    10 |
+-------+
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> drop procedure test_while;
Query OK, 0 rows affected (0.00 sec)

WHILE Statement

The WHILE statement is another mechanism to loop over a set of statements until a condition is true.

[begin_label:] WHILE search_condition DO
    statement_list
END WHILE [end_label]