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