Delete duplicate records in SQL Server?

sql tsql duplicates delete-row

usr021986 · Jul 23, 2010 · Viewed 97.3k times · Source

Consider a column named EmployeeName table Employee. The goal is to delete repeated records, based on the EmployeeName field.

EmployeeName
------------
Anand
Anand
Anil
Dipak
Anil
Dipak
Dipak
Anil

Using one query, I want to delete the records which are repeated.

How can this be done with TSQL in SQL Server?

Answer

You can do this with window functions. It will order the dupes by empId, and delete all but the first one.

delete x from (
  select *, rn=row_number() over (partition by EmployeeName order by empId)
  from Employee 
) x
where rn > 1;

Run it as a select to see what would be deleted:

select *
from (
  select *, rn=row_number() over (partition by EmployeeName order by empId)
  from Employee 
) x
where rn > 1;