Stats.jsp uses slightly incorrect SQL query with nonaggregated column. It's not compatible with default MySQL settings anymore.

[Nable80]

MySQL 5.5 was more permissive but 5.7 has finally uncovered this problem.

E.g.:

select nick, user_id, reg, COUNT(*) cnt from x_mipt_cc_messages
where msgDate BETWEEN (NOW() - INTERVAL 1 DAY) AND NOW()
group by nick
order by cnt desc;
-- ERROR 1055 (42000): Expression #2 of SELECT list is not in GROUP BY clause
-- and contains nonaggregated column 'xonix_search.x_mipt_cc_messages.user_id'
-- which is not functionally dependent on columns in GROUP BY clause;
-- this is incompatible with sql_mode=only_full_group_by

There is a dirty workaround but I don't want it to become a permanent solution:

[mysqld]
sql_mode = "STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION"