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MySQL query to find duplicate tuples and display the count?
To find duplicate tuples, use GROUP BY HAVING clause. Let us first create a table −
mysql> create table DemoTable -> ( -> Id int, -> Name varchar(20) -> ); Query OK, 0 rows affected (0.80 sec)
Insert some records in the table using insert command −
mysql> insert into DemoTable values(100,'Chris'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable values(101,'David'); Query OK, 1 row affected (0.23 sec) mysql> insert into DemoTable values(101,'Mike'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values(100,'Carol'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable values(100,'Chris'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values(100,'Chris'); 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 −
+------+-------+ | Id | Name | +------+-------+ | 100 | Chris | | 101 | David | | 101 | Mike | | 100 | Carol | | 100 | Chris | | 100 | Chris | +------+-------+ 6 rows in set (0.00 sec)
Following is the query to find duplicate tuples −
mysql> select Id,Name,count(*) as t from DemoTable -> group by Id,Name -> having count(*) > 2;
This will produce the following output −
+------+-------+---+ | Id | Name | t | +------+-------+---+ | 100 | Chris | 3 | +------+-------+---+ 1 row in set (0.03 sec)
Updated on: 26-Feb-2020
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