Pro-DBA here. Not sure why you're being downvoted. I know what you're getting at. Different vendor SQL engines and query optimisers behave differently. There's

Pro-DBA here. Not sure why you're being downvoted. I know what you're getting at. Different vendor SQL engines and query optimisers behave differently. There's isn't really a silver bullet for all database engines past the simple and obvious stuff like making sure columns you query most have indexes. Once you've exhausted these tuning options you really need to know your specific database engine's internals.