Merge pull request #5016 from opf/fix/group_by_custom_field

'fix' grouping by custom field

config/database.yml.example

@@ -43,6 +43,11 @@ development:
   username: root
   password:
   encoding: utf8
+  variables:
+    # These are the default MySql Modes for rails 5.0 only excluding
+    # ONLY_FULL_GROUP_BY which would interfere with the current implementation
+    # of the query grouping by custom fields.
+    sql_mode: "no_auto_value_on_zero,strict_trans_tables,strict_all_tables,no_zero_in_date,no_zero_date,error_for_division_by_zero,no_auto_create_user,no_engine_substitution"
 
 # Warning: The database defined as "test" will be erased and
 # re-generated from your development database when you run "rake".