Conditional WHERE clause in MySQL stored procedure to set a custom value for NULL values

To set a custom value for NULL values, use the UPDATE command along with IS NULL property in a stored procedure. Let us first create a table −

mysql> create table DemoTable
(
   Id int,
   FirstName varchar(50)
);
Query OK, 0 rows affected (0.67 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable values(100,'Chris');
Query OK, 1 row affected (0.18 sec)
mysql> insert into DemoTable values(101,NULL);
Query OK, 1 row affected (0.20 sec)
mysql> insert into DemoTable values(102,'Mike');
Query OK, 1 row affected (0.38 sec)
mysql> insert into DemoTable values(103,NULL);
Query OK, 1 row affected (0.74 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable;

This will produce the following output −

+------+-----------+
| Id   | FirstName |
+------+-----------+
| 100  | Chris     |
| 101  | NULL      |
| 102  | Mike      |
| 103  | NULL      |
+------+-----------+
4 rows in set (0.00 sec)

Following is the query to create a stored procedure −

mysql> DELIMITER //
mysql> create procedure where_clauseProc()
   BEGIN
   update DemoTable set FirstName='Robert' where FirstName IS NULL;
   END //
Query OK, 0 rows affected (4.11 sec)
mysql> DELIMITER ;

Call the stored procedure using CALL command −

mysql> call where_clauseProc();
Query OK, 2 rows affected (0.10 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable;

This will produce the following output −

+------+-----------+
| Id   | FirstName |
+------+-----------+
| 100  | Chris     |
| 101  | Robert    |
| 102  | Mike      |
| 103  | Robert    |  
+------+-----------+
4 rows in set (0.00 sec)