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How to find repeated rows and display there count in a separate column with 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)
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