Database
db={"songs":[{songName:"In Da Club",_id:ObjectId("5a934e000102030405000001")},{songName:"Happy Birthday",_id:ObjectId("5a934e000102030405000002")},{songName:"Ode to Joy",_id:ObjectId("5a934e000102030405000003")}],"playlists":[{_id:ObjectId("5a934e000102030405000004"),playlistName:"PlaylistOne",songs:[ObjectId("5a934e000102030405000001"),ObjectId("5a934e000102030405000009")]},{_id:ObjectId("5a934e000102030405000005"),playlistName:"PlaylistTwo",songs:[ObjectId("5a934e000102030405000001")]}]}
Query
db.songs.aggregate([{$match:{songName:"In Da Club"}},{$lookup:{from:"playlists",localField:"_id",foreignField:"songs",as:"playlists"}}])