Table joins was the only thing that beat me down when I used to use Class::DBI (that and some instability issues when I used it under mod_perl).
I've been asked to write more comparison related information in my documentation for Sql::Simple, not realizing how many people are trying to solve this irritating problem.

Any sql module that lets you treat a database as a large data structure to do something wacky like any kind of transform is cool. (imho) Nice post.

cheers,
Ryan Dietrich (my friends call me dextius)