What version of Snort? Snort hasn't supported direct database inserts for some time now, you need to use Unified2 output instead, and have your choice of Unified2 tool (Barnyard2 or Pigsty usually) handle the database insertion.
Oh, so the guide I followed is outdated. I installed Snort 2.7.0.
That's very, very old - from 2007. Try the current version, 2.9.7.3 (or Suricata 2.0.4).