diff --git a/superset/connectors/sqla/models.py b/superset/connectors/sqla/models.py
index c19f01fb2c..c3d440a624 100644
--- a/superset/connectors/sqla/models.py
+++ b/superset/connectors/sqla/models.py
@@ -1092,16 +1092,16 @@ class SqlaTable(Model, BaseDatasource):  # pylint: disable=too-many-public-metho
             columns = groupby or columns
             for selected in columns:
                 # if groupby field/expr equals granularity field/expr
-                table_col = columns_by_name.get(selected)
-                if table_col and table_col.type_generic == GenericDataType.TEMPORAL:
-                    outer = table_col.get_timestamp_expression(
+                if selected == granularity:
+                    sqla_col = columns_by_name[selected]
+                    outer = sqla_col.get_timestamp_expression(
                         time_grain=time_grain,
                         label=selected,
                         template_processor=template_processor,
                     )
                 # if groupby field equals a selected column
-                elif table_col:
-                    outer = table_col.get_sqla_col()
+                elif selected in columns_by_name:
+                    outer = columns_by_name[selected].get_sqla_col()
                 else:
                     outer = literal_column(f"({selected})")
                     outer = self.make_sqla_column_compatible(outer, selected)