EXCEPT when the second set fully covers the first

Question

Accepted Answer

EXCEPT removes from the first set any row that exists in the second set. Both A101 and B202 appear in discontinued, so both are removed. The result is empty - every product in the first set was found in the second set. C303 only appears in discontinued, so it is not part of the first query and never shows up. Order matters with EXCEPT: switching the two queries would return C303, not an empty set.