From: Matt H <matt@...>
Date: 2009-10-25T05:34:39+09:00
Subject: Re: Help with SQL -> associations (Multiple JOINs)

On Saturday, October 24, 2009, Gleb Mazovetskiy <glex.spb@gmail.com> wrote:
> Is there a way to express this with associations?
>
>     @songs = Song.find_by_sql(%Q{
>             SELECT songs.*, song_playlist_relationships.playlist_id
>             FROM songs INNER JOIN song_playlist_relationships
>               ON songs.id = song_playlist_relationships.song_id
>               WHERE song_playlist_relationships.playlist_id IN
> (#{@playlists.collect{|p| p.id}.join(',')})})
>

Something like this should work. Double-check the :joins option in the
Rails documentation. I might have it wrong.

playlist_ids = @playlists.collect{|p| p.id}
Song.find(:all,
  :conditions => ["song_playlists_relationships.playlist_id IN (?)",
playlist_ids],
  :joins => :song_playlist_relationships)


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