slick(play-slick)3.0を使ったjoinの方法

zip_join.scala

    val q = for {
      (user, pao) <- usrs.soft joinLeft paos.soft on (_.id === _.userId)
      (pao, pa) <- paos.soft join pas.soft on (_.paId === _.id)
    } yield (user, pao, pa)

    db.run(q.result) map {
      case Seq(data) => Seq(data._1.copy(pa = Some(data._3)))
      case _ => Seq()
    }