Question

Basically I have three models songs, playlists and assignments.

Songs have many playlists through assignments, and vice versa.

I want to write a query that finds every playlist that contains a specified song. Let’s say that song is specified by @song.

So far I’ve got:

#find all the assignments that contain a song_id 

@commonAssignments = Assignment.where("song_id = ?", @data)
@commonPlaylists = #code to find playlists which contain any of the assignments found here

I was wondering where to go from here, thanks for any help in advance

Answer 1

#create an array of strings made up of playlist id's

@commonAssignments = Assignment.select(:playlist_id).where("song_id = ?", @data).map &:setlist_id

#then find all records associated
    @commonPlaylists = Playlist.find(@commonAssignments)