MySQL Aggregate Function to find the number of occurrences?

To count the number of occurrences from a table, you can use aggregate function COUNT() with GROUP BY. The syntax is as follows −

SELECT yourColumnName,COUNT(*) as anyVariableName from yourTableName GROUP BY yourColumnName;

To understand the above syntax, let us create a table. The query to create a table is as follows −

mysql> create table CountOccurrences
   -> (
   -> CarId int not null auto_increment,
   -> CarName varchar(30),
   -> PRIMARY KEY(CarId)
   -> );
Query OK, 0 rows affected (0.68 sec)

Insert some records in the table using insert command. The query is as follows −

mysql> insert into CountOccurrences(CarName) values('Aston Martin');
Query OK, 1 row affected (0.10 sec)

mysql> insert into CountOccurrences(CarName) values('BMW');
Query OK, 1 row affected (0.20 sec)

mysql> insert into CountOccurrences(CarName) values('Aston Martin');
Query OK, 1 row affected (0.15 sec)

mysql> insert into CountOccurrences(CarName) values('Honda');
Query OK, 1 row affected (0.20 sec)

mysql> insert into CountOccurrences(CarName) values('BMW');
Query OK, 1 row affected (0.11 sec)

mysql> insert into CountOccurrences(CarName) values('Audi');
Query OK, 1 row affected (0.18 sec)

mysql> insert into CountOccurrences(CarName) values('Aston Martin');
Query OK, 1 row affected (0.11 sec)

mysql> insert into CountOccurrences(CarName) values('Bugatti');
Query OK, 1 row affected (0.22 sec)

mysql> insert into CountOccurrences(CarName) values('BMW');
Query OK, 1 row affected (0.27 sec)

mysql> insert into CountOccurrences(CarName) values('Honda');
Query OK, 1 row affected (0.13 sec)

mysql> insert into CountOccurrences(CarName) values('Audi');
Query OK, 1 row affected (0.13 sec)

mysql> insert into CountOccurrences(CarName) values('BMW');
Query OK, 1 row affected (0.12 sec)

Display all records from the table using select statement. The query is as follows −

mysql> select *from CountOccurrences;

The following is the output −

+-------+--------------+
| CarId | CarName      |
+-------+--------------+
|     1 | Aston Martin |
|     2 | BMW          |
|     3 | Aston Martin |
|     4 | Honda        |
|     5 | BMW          |
|     6 | Audi         |
|     7 | Aston Martin |
|     8 | Bugatti      |
|     9 | BMW          |
|    10 | Honda        |
|    11 | Audi         |
|    12 | BMW          |
+-------+--------------+
12 rows in set (0.00 sec)

The following is the query to count the number of occurrences of each value in a column using count() with GROUP BY −

mysql> select CarName,count(*) as TotalCount from CountOccurrences
   -> group by CarName;

The following is the output −

+--------------+------------+
| CarName      | TotalCount |
+--------------+------------+
| Aston Martin |          3 |
| BMW          |          4 |
| Honda        |          2 |
| Audi         |          2 |
| Bugatti      |          1 |
+--------------+------------+
5 rows in set (0.00 sec)

Ankith Reddy

Published on 31-Jan-2019 11:37:07

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