MySQL Select where value exists more than once
For this, you can use GROUP BY HAVING along with the COUNT(*) function. Let us first create a table −
mysql> create table DemoTable
-> (
-> Value int
-> );
Query OK, 0 rows affected (0.47 sec)
Insert some records in the table using insert command −
mysql> insert into DemoTable values(20);
Query OK, 1 row affected (0.18 sec)
mysql> insert into DemoTable values(10);
Query OK, 1 row affected (0.08 sec)
mysql> insert into DemoTable values(30);
Query OK, 1 row affected (0.12 sec)
mysql> insert into DemoTable values(10);
Query OK, 1 row affected (0.16 sec)
mysql> insert into DemoTable values(30);
Query OK, 1 row affected (0.12 sec)
mysql> insert into DemoTable values(40);
Query OK, 1 row affected (0.12 sec)
mysql> insert into DemoTable values(50);
Query OK, 1 row affected (0.27 sec)
Display all records from the table using select statement −
mysql> select *from DemoTable;
This will produce the following output −
+-------+
| Value |
+-------+
| 20 |
| 10 |
| 30 |
| 10 |
| 30 |
| 40 |
| 50 |
+-------+
7 rows in set (0.00 sec)
Following is the query to select where value exists more than once −
mysql> select *from DemoTable
-> group by Value
-> having count(*) > 1;
This will produce the following output −
+-------+
| Value |
+-------+
| 10 |
| 30 |
+-------+
2 rows in set (0.38 sec)
Published on 13-Dec-2019 05:39:40
