Using DISTINCT and COUNT together in a MySQL Query?

We can use DISTINCT and COUNT together in a single MySQL query. Firstly, let us create a table. The CREATE command is used to create a table.

mysql> create table DistCountDemo
   - > (
   - > id int,
   - > name varchar(100),
   - > age int
   - > );
Query OK, 0 rows affected (0.48 sec)

Records are inserted with the help of INSERT command.

mysql> insert into DistCountDemo values(1,'John',23);
Query OK, 1 row affected (0.11 sec)

mysql> insert into DistCountDemo values(2,'Bob',24);
Query OK, 1 row affected (0.14 sec)

mysql> insert into DistCountDemo values(3,'John',23);
Query OK, 1 row affected (0.16 sec)

mysql> insert into DistCountDemo values(4,'Carol',23);
Query OK, 1 row affected (0.20 sec)

To display all records with the help of the SELECT statement.

mysql> select *from DistCountDemo;

The following is the output.

+------+-------+------+
| id   | name  | age  |
+------+-------+------+
|    1 | John  |   23 |
|    2 | Bob   |   24 |
|    3 | John  |   23 |
|    4 | Carol |   23 |
+------+-------+------+
4 rows in set (0.00 sec)

Applying COUNT as well as DISTINCT to find out the number of students with age 23.

mysql> SELECT COUNT(DISTINCT name) from  DistCountDemo WHERE age=23;

The following is the output.

+----------------------+
| COUNT(DISTINCT name) |
+----------------------+
|                    2 |
+----------------------+
1 row in set (0.05 sec)