Hi, I have a very large query that extracts data from multiple databases and provides a data set of assets. I need to check these assets against another table to see if they are present there. Unfortunately each row has no unique identifier in the query. The table I'm checking against also has no unique identifier. I have tried to use the set operator MINUS.. Select 6 columns from the first query Minus The same 6 columns from the checking table. This does provide a result set, but to check if it was correct I limited the first query and the checking table via 'WHERE' criteria to display the same two rows and then used MINUS but it did not leave me with 0 rows as expected but two rows. I wondered why this could be? Also is MINUS the best way to do this.. I've been told to perform a left outer join on multiple columns between the two tables?? Thanks, R.