SELECT w.slug FROM whisky w LEFT JOIN whisky_words ww ON (w._id = ww.whisky_id) WHERE ww.word = 'glenfiddich'

name: "Glenfiddich 12", slug: "glenfiddich-12", words: [ "glenfiddich", "12" ],

db.whisky.find( { words: 'glenfiddich' }, { slug: 1 } ).pretty();