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)
Published on 23-Aug-2019 08:29:34
