How to delete all duplicate records from SQL Table?

Question

Hello I have table name FriendsData that contains duplicate records as shown below

fID UserID  FriendsID       IsSpecial      CreatedBy
---         


        

Answer 1

It seems counter-intuitive, but you can delete from a common table expression (under certain circumstances). So, I'd do it like so:

with cte as (
  select *, 
     row_number() over (partition by userid, friendsid order by fid) as [rn]
  from FriendsData
)
delete cte where [rn] <> 1

This will keep the record with the lowest fid. If you want something else, change the order by clause in the over clause.

If it's an option, put a uniqueness constraint on the table so you don't have to keep doing this. It doesn't help to bail out a boat if you still have a leak!