How to count null values in MySQL?

To count null values in MySQL, you can use CASE statement. Let us first see an example and create a table −

mysql> create table DemoTable (    Id int NOT NULL AUTO_INCREMENT PRIMARY KEY,    FirstName varchar(20) ); Query OK, 0 rows affected (0.77 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable(FirstName) values('John'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable(FirstName) values(null); Query OK, 1 row affected (0.25 sec) mysql> insert into DemoTable(FirstName) values(''); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable(FirstName) values('Larry'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable(FirstName) values(''); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable(FirstName) values(null); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable(FirstName) values(null); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable(FirstName) values('Bob'); Query OK, 1 row affected (0.15 sec)

Following is the query to display all records from the table using select statement −

mysql> select *from DemoTable;

This will produce the following output −

+----+-----------+ | Id | FirstName | +----+-----------+ | 1  | John | | 2 | NULL | | 3 | | | 4 | Larry | | 5 | | | 6 | NULL | | 7 | NULL | | 8 | Bob | +----+-----------+ 8 rows in set (0.00 sec)

Here is the query to count Null values in MySQL −

mysql> select sum(case when FirstName IS NULL then 1 else 0 end) as NUMBER_OF_NULL_VALUE from DemoTable;

This will produce the following output −

+----------------------+ | NUMBER_OF_NULL_VALUE | +----------------------+ | 3 | +----------------------+ 1 row in set (0.00 sec)