How to delete duplicate rows in SQL Server?

Question

How can I delete duplicate rows where no unique row id exists?

My table is

col1  col2 col3 col4 col5 col6 col7
john  1          


        

Answer 1

Microsoft has a vey ry neat guide on how to remove duplicates. Check out http://support.microsoft.com/kb/139444

In brief, here is the easiest way to delete duplicates when you have just a few rows to delete:

SET rowcount 1;
DELETE FROM t1 WHERE myprimarykey=1;

myprimarykey is the identifier for the row.

I set rowcount to 1 because I only had two rows that were duplicated. If I had had 3 rows duplicated then I would have set rowcount to 2 so that it deletes the first two that it sees and only leaves one in table t1.

Hope it helps anyone