A few months back I ran across this article for checking semantic equivalencies of queries. That’s interesting, from the perspective of someone that has once or twice rewritten a query to be faster and then discovered it was subtly different. I don’t think we have the equivalent. We can compare query plans hashes, but often the goal is to get a different plan. We can compare the query hashes, but the goal is to write the query differently! Comparing the results across a range of scenarios is usually the simplest option, but it sure would be nice to compare two queries and know they would return the same results.