private void setJoinType() {
    if ( operator.getType() == SubQueryType.NOT_IN ||
        operator.getType() == SubQueryType.NOT_EXISTS ) {
      joinType = JoinType.LEFTOUTER;
    } else {
      joinType = JoinType.LEFTSEMI;
    }
  }
@param parentQueryRR
@param forHavingClause
@param outerQueryAlias
@return true if it is correlated scalar subquery with an aggregate
@throws SemanticException
ql/src/java/org/apache/hadoop/hive/ql/parse/QBSubQuery.java