I’ve never seen a “never ending SQL request” My only guess there is that you’ve somehow created an infinite loop in the SQL syntax, something else that I don’t recall ever seeing. My only guess is that’s is cause where you’re trying to match rows.
I dislike giving up, but I think you’ve gone further than my ability to help, and maybe you’re trying to do something that WP can’t do, but I can’t say.
More than likely, if this was something that I had to complete I would give up on doing it with a query at this point. I’d instead look at loading all of the data into a multidimensional array, or possibly multiple arrays, and then use PHP to build something that could do the searching.
I’m really sorry I can’t help more.
