ASA SQL User's Guide
Summarizing, Grouping and Sorting Query Results
Performing set operations on query results with UNION, INTERSECT, and EXCEPT
The EXCEPT operation lists the differences between two result sets. The following general construction lists all those rows that appear in the result set of query-1, but not in the result set of query-2.
query-1
EXCEPT
query-2
The INTERSECT operation lists the rows that appear in each of two result sets. The following general construction lists all those rows that appear in the result set of both query-1 and query-2.
query-1
INTERSECT
query-2
Like the UNION operation, both EXCEPT and INTERSECT take the ALL modifier, which prevents the elimination of duplicate rows from the result set.
For more information, see EXCEPT operation, and INTERSECT operation.