Check if two “select”s are equivalent

Question

Is there a way to check if two (non-trivial) select are equivalent?

Initially I was hoping for a formally equivalence between two selects, but the answers in proving

Answer 1

If you want to compare the query results try the following:

(select * from query1 MINUS select * from query2) 
UNION ALL
(select * from query2 MINUS select * from query1)

This will result in all rows that are returned by only one of the queries.