1.When table has Identity Column Delete from TBLABC
where ID not in (Select Max(ID) from TBLABC group by A,B,C )
2. With Common Table Expression by Using ROW_NUMBER() with[TBLXYZ] AS
(
Select Row_Number() over(PARTITION BY a,b,c order by a ) as RowID,* from TBLABC
)
Delete from TBLXYZ where RowID > 1
Note-The RowID column returns value greeter than 1 for duplicate Rows.