public boolean containsQueryWithoutSourceTable() {
    if (qb != null) {
      return qb.containsQueryWithoutSourceTable();
    } else {
      return qbexpr1.containsQueryWithoutSourceTable() || qbexpr2.containsQueryWithoutSourceTable();
    }
  }
returns true, if the query block contains any query, or subquery without a source table
Like select current_user(), select current_database()
@return true, if the query block contains any query without a source table
ql/src/java/org/apache/hadoop/hive/ql/parse/QBExpr.java