Find Repeated Rows and Display Count in MySQL

For this, use the GROUP BY HAVING clause. Let us first create a table −

mysql> create table DemoTable(
   Name varchar(100),
   Age int
);
Query OK, 0 rows affected (1.50 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable values('Chris',23);
Query OK, 1 row affected (0.20 sec)
mysql> insert into DemoTable values('David',21);
Query OK, 1 row affected (0.14 sec)
mysql> insert into DemoTable values('Chris',23);
Query OK, 1 row affected (0.17 sec)
mysql> insert into DemoTable values('Chris',21);
Query OK, 1 row affected (0.27 sec)
mysql> insert into DemoTable values('Mike',25);
Query OK, 1 row affected (0.17 sec)
mysql> insert into DemoTable values('David',21);
Query OK, 1 row affected (0.10 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable;

This will produce the following output −

+-------+------+
| Name  | Age  |
+-------+------+
| Chris | 23   |
| David | 21   |
| Chris | 23   |
| Chris | 21   |
| Mike  | 25   |
| David | 21   |
+-------+------+
6 rows in set (0.00 sec)

Following is the query to find repeated rows and display count in a separate column −

mysql> select Name,Age,count(*) AS Repeated from DemoTable
group by Name,Age
having Repeated > 1;

This will produce the following output −

+-------+------+----------+
| Name  | Age  | Repeated |
+-------+------+----------+
| Chris | 23   | 2        |
| David | 21   | 2        |
+-------+------+----------+
2 rows in set (0.00 sec)