Count occurrences of known distinct values in MySQL

For this, you can use aggregate function SUM(). Let us first create a table −

mysql> create table DemoTable636 (    StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY,StudentFirstName varchar(100) ); Query OK, 0 rows affected (0.51 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable636(StudentFirstName) values('John'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable636(StudentFirstName) values('Robert'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable636(StudentFirstName) values('Robert'); Query OK, 1 row affected (0.22 sec) mysql> insert into DemoTable636(StudentFirstName) values('Sam'); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable636(StudentFirstName) values('Mike'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable636(StudentFirstName) values('John'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable636(StudentFirstName) values('Robert'); Query OK, 1 row affected (0.16 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable636;

This will produce the following output −

+-----------+------------------+ | StudentId | StudentFirstName | +-----------+------------------+ |         1 | John             | |         2 | Robert           | |         3 | Robert           | |         4 | Sam              | |         5 | Mike             | |         6 | John             | |         7 | Robert           | +-----------+------------------+ 7 rows in set (0.00 sec)

Following is the query to count occurrences of known (or enumerated) distinct values −

mysql> select    sum(StudentFirstName='John') AS JOHN_COUNT,    sum(StudentFirstName='Robert') AS ROBERT_COUNT,    sum(StudentFirstName='Sam') AS SAM_COUNT,    sum(StudentFirstName='Mike') AS MIKE_COUNT    from DemoTable636;

This will produce the following output −

+------------+--------------+-----------+------------+ | JOHN_COUNT | ROBERT_COUNT | SAM_COUNT | MIKE_COUNT | +------------+--------------+-----------+------------+ |          2 |            3 | 1         | 1          | +------------+--------------+-----------+------------+ 1 row in set (0.00 sec)