Only yesterday I kinda messed up in an interview because I wasn't good at SQL. Just cursorily checked the link you posted and it is looking good. Thanks for the suggestion.
Can you remember the questions? I think that I'm relatively good with SQL, but I just realized, I have never been asked any SQL specific questions, even though most of my work has been tied to it. The questions usually revolve around specifics of the engine, not query language itself.