Wednesday, April 15, 2015

Delete duplicate records from table in single statement (SQL Server)

Deleting duplicate records is very common requirement therefore multiple options are available to delete duplicate records. However this article provides the solution to delete the duplicate records using single statement.

Delete from <TABLE_NAME> where <ID> not in ( select max(<ID>) from TABLE_NAME> group by <DUPLICATE_COLUMN>)



For example:

Employee table
EmpId
EmpFullName
EmpSalary
EmpTitle
1
Sumit Bajaj
5000
Dev
2
Amit
10000
SDev
3
Sumit Bajaj
5000
Dev
4
Priyanka
50000
Mgr
5
Umesh
10000
SDev
6
Umesh
10000
SDev
7
Amit
10000
SDev
8
Geetika
5000
Dev

where few records are duplicate and need to be removed.

For this table, delete query would be 

Delete from Employee where EmpId not in (select max(EmpId) from Employee group by EmpFullName)

After executing this query you will left with only unique records as shown below.

EmpId
EmpFullName
EmpSalary
EmpTitle
3
Sumit Bajaj
5000
Dev
4
Priyanka
50000
Mgr
6
Umesh
10000
SDev
7
Amit
10000
SDev
8
Geetika
5000
Dev

Thanks for reading and hope this article helped.