implicit class QueryExtension2[T, E](val query1: Query[T, E, Seq]) {
    def left[T2, E2](query2: Query[T2, E2, Seq])(implicit condition: (T, T2) => Column[Boolean]): Query[(T, T2), (E, E2), Seq] =
      query1.leftJoin(query2).on(condition)
  }


 implicit def joinCondition1 = (r: Radnik, rp: Radproj) => r.mbr === rp.mbr
  implicit def joinCondition2 = (join: (Radnik, Radproj), p: Projekat) => join._2.spr === p.spr


 val query5 = for {
   ((r, rp), p) <- Radnik left Radproj  left Projekat
   if ime.map(r.ime === _).getOrElse(r.ime =!= "") && prz.map(r.prz === _).getOrElse(r.prz =!= "")
   || spr.map(rp.spr ===_).getOrElse(rp.spr =!= -1)
 } yield (r.ime, r.prz, p.nap)