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In MySQL stored procedures, how to check if a local variable is null?
For this, use COALESCE(). Let us implement a stored procedure to check if the local variable is null −
mysql> DELIMITER //
mysql> CREATE PROCEDURE local_VariableDemo()
BEGIN
DECLARE value1 int;
DECLARE value2 int;
select value1,value2;
select
concat('After checking local variable is null the sum is = ',COALESCE(value1,0)+COALESCE(value2,0));
END
//
Query OK, 0 rows affected (0.19 sec)
mysql> DELIMITER ;Call the stored procedure using CALL command −
mysql> call local_VariableDemo();
This will produce the following output −
+--------+--------+
| value1 | value2 |
+--------+--------+
| NULL | NULL |
+--------+--------+
1 row in set (0.00 sec)
+-----------------------------------------------------------------------------------------------------+
| concat('After checking local variable is null the sum is = ',COALESCE(value1,0)+COALESCE(value2,0)) |
+-----------------------------------------------------------------------------------------------------+
| After checking local variable is null the sum is = 0 |
+-----------------------------------------------------------------------------------------------------+
1 row in set (0.01 sec)
Query OK, 0 rows affected (0.03 sec)
Updated on: 03-Oct-2019
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