Sử dụng user variable trong MySQL stored procedure

User variable trong procedure tham chiếu bằng dấu @ prefix (ví dụ @A, @B).

Ví dụ procedure Proc_Uservariables:

mysql> DELIMITER //
mysql> CREATE PROCEDURE Proc_Uservariables()
    -> BEGIN
    -> SET @A = 100;
    -> SET @B = 500;
    -> SELECT @A, @B, @A+@B;
    -> END //
Query OK, 0 rows affected (0.00 sec)
mysql> DELIMITER ;

mysql> CALL Proc_Uservariables();
+------+------+-------+
| @A   | @B   | @A+@B |
+------+------+-------+
| 100  | 500  | 600   |
+------+------+-------+
1 row in set (0.00 sec)