hi friend,

Suppose the table is as follows :

id    name     age
1    deepak    23
2    ankit     23
3    sharma    24
4    kaushal   25
5    Akumar    26
6    Bkumar    30
7    Ckumar    26
8    Dkumar    23
9    deepak    30

You can write the query for retrieving the duplicate records in the above table as follows :

SELECT age
FROM employee
GROUP BY age
HAVING COUNT(*)>1

The above query will return the records of age which are entered multiple times i.e. there are duplicate records of age in the employee table