private Query createParticipantsDeleteQuery(final Long workoutId, final Set<Long> participants) {
   final SQLHelper.Predicate idPred =
       createInListPredicate("USER_ID", participants, "participant");
   final Query query =
       entityManager.createNativeQuery(
           "delete FROM WORKOUT_USER WHERE WORKOUT_ID = :workoutId AND " + idPred);
   query.setParameter("workoutId", workoutId);
   idPred.bindVariables(query);
   return query;
 }
 private Query createParticipantsInsertUnionQuery(
     final Long workoutId, final Set<Long> participants) {
   final SQLHelper.Predicate listPred = createInListPredicate("ID", participants, "participant");
   final Query query =
       entityManager.createNativeQuery(
           "insert INTO WORKOUT_USER (USER_ID, WORKOUT_ID) SELECT ID, :workoutId FROM USERS WHERE"
               + " ID not in (select USER_ID from WORKOUT_USER where WORKOUT_ID = :workoutId) and "
               + listPred);
   query.setParameter("workoutId", workoutId);
   listPred.bindVariables(query);
   return query;
 }