title: best way to get good with sql queries
body: <p>As a programmer I would like to get a strong hold on writing queries.  In my college years I've read a few sql books and rest I've just learned working as a programmer for last couple of years.  But as those queries were work related...they weren't that 'hard' or complex.  </p>
  
  <p>what would you guys suggest ? Is there a good advanced sql book that would teach and then test the knowledge by giving some questions?</p>
  
  <p>Thanks!</p>