This plugin for Squeezebox Server makes it possible to create smart
playlists. Although the standard Squeezebox Server doesn't support
smart playlists by itself, together with iTunes and the standard
Squeezebox Server iTunes integration, it is possible to use smart
playlists defined in iTunes. The problem though is that the integrated
iTunes smart playlists will not be recalculated until the next time
you perform a rescan in Squeezebox Server. The SQL Playlist plugin
takes care of this problem and implements native smart playlist in
Squeezebox Server without any need to use iTunes. The smart playlists
implemented in SQL Playlist will also be automatically re-calculated
after each track played so they will be based on the latest statistic
information.

A smart playlist in SQL Playlist are continous and will run forever in
the same way as the standard Random Mix plugin, you can optionally
also choose that a smart playlist shouldn't repeat already played
tracks and in that case the music will stop when all songs matching
the playlist has been played.

WWW: http://wiki.slimdevices.com/index.php/SQL_Playlist_plugin