How to count the distinct column in MySQL?

You need to use GROUP BY for this. Let us first create a table −

mysql> create table DemoTable
   (
   StudentFirstName varchar(20)
   );
Query OK, 0 rows affected (0.74 sec)

Insert records in the table using insert command −

mysql> insert into DemoTable values('John');
Query OK, 1 row affected (1.34 sec)
mysql> insert into DemoTable values('Carol');
Query OK, 1 row affected (0.28 sec)
mysql> insert into DemoTable values('John');
Query OK, 1 row affected (0.14 sec)
mysql> insert into DemoTable values('John');
Query OK, 1 row affected (0.14 sec)
mysql> insert into DemoTable values('Bob');
Query OK, 1 row affected (0.25 sec)
mysql> insert into DemoTable values('David');
Query OK, 1 row affected (0.55 sec)
mysql> insert into DemoTable values('Bob');
Query OK, 1 row affected (0.08 sec)
mysql> insert into DemoTable values('Carol');
Query OK, 1 row affected (0.37 sec)
mysql> insert into DemoTable values('Robert');
Query OK, 1 row affected (0.14 sec)

Display all records from the table using select statement −

mysql> select * from DemoTable;

This will produce the following output −

+------------------+
| StudentFirstName |
+------------------+
| John             |
| Carol            |
| John             |
| John             |
| Bob              |
| David            |
| Bob              |
| Carol            |
| Robert           |
+------------------+
9 rows in set (0.00 sec)

Here is the query to count the distinct column in MySQL −

mysql> select StudentFirstName,count(*) from DemoTable
group by StudentFirstName;

This will produce the following output −

+------------------+----------+
| StudentFirstName | count(*) |
+------------------+----------+
| John             | 3        |
| Carol            | 2        |
| Bob              | 2        |
| David            | 1        |
| Robert           | 1        |
+------------------+----------+
5 rows in set (0.00 sec)