How to check if data is NULL in MySQL?

You can use IF() to check if data is NULL.  Let us first create a table −

mysql> create table DemoTable (    Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,    Name varchar(200),    Age int ); Query OK, 0 rows affected (0.44 sec)

Insert records in the table using insert command −

mysql> insert into DemoTable(Name,Age) values('John',23); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable(Name,Age) values('Sam',null); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable(Name,Age) values('Mike',23); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable(Name,Age) values('David',21); Query OK, 1 row affected (0.21 sec) mysql> insert into DemoTable(Name,Age) values('Carol',null); Query OK, 1 row affected (0.13 sec)

Display records from the table using select command −

mysql> select *from DemoTable;

This will produce the following output −

+----+-------+------+ | Id | Name | Age | +----+-------+------+ | 1 | John | 23 | | 2 | Sam | NULL | | 3 | Mike | 23 | | 4 | David | 21 | | 5 | Carol | NULL | +----+-------+------+ 5 rows in set (0.00 sec)

Here is the query to check if data is NULL or not. This adds a message wherever NULL in the record is visible −

mysql> select if(Age IS NULL,'Age is missing',Age) from DemoTable;

This will produce the following output −

+--------------------------------------+ | if(Age IS NULL,'Age is missing',Age) | +--------------------------------------+ | 23                                 | | Age is missing | | 23 | | 21 | | Age is missing | +--------------------------------------+ 5 rows in set (0.00 sec)