MySQL query to display the count of distinct records from a column with duplicate records

Let us first create a table −

mysql> create table DemoTable (    StudentId int,    StudentFirstName varchar(100) ); Query OK, 0 rows affected (0.88 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable values(100,'John'); Query OK, 1 row affected (0.32 sec) mysql> insert into DemoTable values(101,'Chris'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable values(102,'John'); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable values(103,'Sam'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values(104,'Sam'); Query OK, 1 row affected (0.13 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable;

This will produce the following output −

+-----------+------------------+ | StudentId | StudentFirstName | +-----------+------------------+ | 100 | John | | 101 | Chris | | 102 | John | | 103 | Sam | | 104 | Sam | +-----------+------------------+ 5 rows in set (0.00 sec)

Following is the query to display the count of distinct records from a column with duplicate records −

mysql> select count(distinct StudentFirstName) from DemoTable;

This will produce the following output −

+----------------------------------+ | count(distinct StudentFirstName) | +----------------------------------+ | 3 | +----------------------------------+ 1 row in set (0.00 sec)