In subquery use alias to do 'order by' (#795)

* in subqry add orderby metric to select

* add comment

caravel/models.py

@@ -728,6 +728,9 @@ def query(  # sqla
         qry = qry.limit(row_limit)
 
         if timeseries_limit and groupby:
+            # some sql dialects require for order by expressions 
+            # to also be in the select clause
+            inner_select_exprs += [main_metric_expr]
             subq = select(inner_select_exprs)
             subq = subq.select_from(tbl)
             subq = subq.where(and_(*(where_clause_and + inner_time_filter)))