ummmm

gistfile1.rb

['foo', 'bar'].inject(Paste.scoped) {|rel, tag|
  rel.where(id: Tagging.joins(:tag).select(:paste_id).where('tags.name = ?', tag))
}.to_sql

# =>
#   SELECT "pastes".*
#   FROM "pastes"
#   WHERE "pastes"."id" IN (SELECT paste_id FROM "taggings" INNER JOIN "tags" ON "tags"."id" = "taggings"."tag_id" WHERE (tags.name = 'foo'))
#     AND "pastes"."id" IN (SELECT paste_id FROM "taggings" INNER JOIN "tags" ON "tags"."id" = "taggings"."tag_id" WHERE (tags.name = 'bar'))
#