func (e *SelectStatement) IsAggregated() bool {
	return e.selectQProp.isAggregation
}

// AggregateResult - returns the aggregated result after all input
// records have been processed. Applies only to aggregation queries.
func (e *SelectStatement) AggregateResult(output Record) error {
	for i, expr := range e.selectAST.Expression.Expressions {
		v, err := expr.evalNode(nil, e.tableAlias)