I was looking for a way to sharpen my SQL skills a few months ago, and after being annoyed with some of the very, very beginner stuff out there I found this: h

I was looking for a way to sharpen my SQL skills a few months ago, and after being annoyed with some of the very, very beginner stuff out there I found this: http://www.sql-ex.ru/ http://www.sql-ex.ru/ The site can be slow sometimes, but I have found queries/puzzles that (a) have shown me use-cases for functions and capabilities I have never used and (b) can be challenging! Later they apparently focus more on optimization, but I haven't gotten there. (Especially since they have hundreds of these more difficult queries). I've done about 70ish so far. What do you guys think about it? Overall, never going to be useful, or a good resource to get better with SQL?