Count Occurrences of Specific Records in MySQL Query

For this, use aggregate function COUNT() and GROUP BY to group those specific records for occurrences. Let us first create a table −

mysql> create table DemoTable
(
   StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY,
   StudentSubject varchar(40)
);
Query OK, 0 rows affected (5.03 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable(StudentSubject) values('MySQL');
Query OK, 1 row affected (0.78 sec)
mysql> insert into DemoTable(StudentSubject) values('Java');
Query OK, 1 row affected (0.39 sec)
mysql> insert into DemoTable(StudentSubject) values('MySQL');
Query OK, 1 row affected (1.12 sec)
mysql> insert into DemoTable(StudentSubject) values('MongoDB');
Query OK, 1 row affected (0.24 sec)
mysql> insert into DemoTable(StudentSubject) values('Java');
Query OK, 1 row affected (0.45 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable;

This will produce the following output −

+-----------+----------------+
| StudentId | StudentSubject |
+-----------+----------------+
|         1 | MySQL          |
|         2 | Java           |
|         3 | MySQL          |
|         4 | MongoDB        |
|         5 | Java           |
+-----------+----------------+
5 rows in set (0.00 sec)

Following is the query to count the occurrences of specific records (duplicate) in one MySQL query −

mysql> select StudentSubject,count(StudentId) from DemoTable group by StudentSubject;

This will produce the following output −

+----------------+------------------+
| StudentSubject | count(StudentId) |
+----------------+------------------+
| MySQL          |                2 |
| Java           |                2 |
| MongoDB        |                1 |
+----------------+------------------+
3 rows in set (0.00 sec)