Difference Between COUNT and COUNT(column_name) in MySQL

The count(*) returns all rows whether column contains null value or not while count(columnName) returns the number of rows except null rows.

Let us first create a table.

Following is the query

mysql> create table ifNotNullDemo    -> (    -> Name varchar(20)    -> ); Query OK, 0 rows affected (0.54 sec)

Following is the query to insert some records in the table using insert command:

mysql> insert into ifNotNullDemo values('Chris'); Query OK, 1 row affected (0.15 sec) mysql> insert into ifNotNullDemo values(''); Query OK, 1 row affected (0.13 sec) mysql> insert into ifNotNullDemo values('Robert'); Query OK, 1 row affected (0.24 sec) mysql> insert into ifNotNullDemo values(null); Query OK, 1 row affected (0.30 sec) mysql> insert into ifNotNullDemo values(0); Query OK, 1 row affected (0.16 sec)

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

mysql> select *from ifNotNullDemo;

This will produce the following output

+--------+ | Name | +--------+ | Chris | |        | | Robert | | NULL | | 0 | +--------+ 5 rows in set (0.00 sec)

Case 1: Following is the demo of count(*) that includes null as well in the count:

mysql> select count(*) from ifNotNullDemo;

This will produce the following output

+----------+ | count(*) | +----------+ | 5 | +----------+ 1 row in set (0.02 sec)

Case 2: Following is the query for count(columnName).

mysql> select count(Name) from ifNotNullDemo;

This will produce the following output

+-------------+ | count(Name) | +-------------+ | 4           | +-------------+ 1 row in set (0.00 sec)