leftJoin.scala

    def getContentsByUser(userId: UUID, adopted: Boolean = false): Either[UserNotFoundError, List[Content]] = {
      getDatabase withDynSession {
        val subQuery =
          adopted match {
            case false => {
              for {
                uc <- UserContentTable.query if uc.userId === userId.toString && (!uc.adopted.isDefined || !uc.adopted)
                c  <- ContentTable.query if uc.contentId === c.id
              }
                yield (uc, c)
            }
            case true => {
              for {
                uc <- UserContentTable.query if uc.userId === userId.toString && (uc.adopted.isDefined && uc.adopted)
                c  <- ContentTable.query if uc.contentId === c.id
              }
                yield (uc, c)
            }
          }


        val query =
          UserTable.query.filter(_.id === userId.toString)
            .leftJoin(subQuery).on { case (u, (uc, c)) => u.id === uc.userId}
            .map { case (u, (uc, c)) => (u, c.optionProjection) }

        query.list match {
          case Nil => Left(UserNotFoundError(userId))
          case cs => Right(cs.map { case (u, c) => c }.flatten )
        }
     
      }
    }