convert distinct to groupby when not supported

gluon/dal.py

@@ -1457,6 +1457,8 @@ class BaseAdapter(ConnectionPool):
         having = args_get('having', False)
         limitby = args_get('limitby', False)
         for_update = args_get('for_update', False)
+        if not distinct in (True,False) and not groupby:
+            distinct, groupby = False, distinct
         if self.can_select_for_update is False and for_update is True:
             raise SyntaxError, 'invalid select attribute: for_update'
         if distinct is True: