Hi,
Quite new to SQL. I have been asked to query two tables to find which combinations of CustomerID and ProductID exist in one but not the other. I am concatenating the fields in the query to produce a combination I can query ( see below)

This seems to work but takes along time - I'm sure there must be a better way of doing this? Please bear in mind I am a novice in your responses!

select distinct(ProductID),CustomerID from customerpackproduct where

str(ProductID) + str(CustomerID) not in

(select str(ProductID) + str(CustomerID) from customerproduct)

order by customerid