GROUP BY issue

[yuliu]

The error has been seen in phpBB users module:

1055 - Expression #2 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'XXX.u.user_type' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by

This affects MySQL with sql_mode only_full_group_by enabled, PostgresSQL and probably SQLite.