MariaDB [test]> create table tt(id int primary key, a int, b int);

Query OK, 0 rows affected (0.28 sec)

MariaDB [test]> select @@sql_mode;

+-------------------------------------------------------------------------------------------+

| @@sql_mode                                                                                |

+-------------------------------------------------------------------------------------------+

| STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |

+-------------------------------------------------------------------------------------------+

1 row in set (0.00 sec)

MariaDB [test]> select a,coalesce(b,1)*a from tt group by a,coalesce(b,1);

Empty set (0.00 sec)

MariaDB [test]> set sql_mode=only_full_group_by;

Query OK, 0 rows affected (0.00 sec)

MariaDB [test]> select a,coalesce(b,1)*a from tt group by a,coalesce(b,1);

ERROR 1055 (42000): 'test.tt.b' isn't in GROUP BY

MariaDB [test]> select a, floor(b) from tt group by a, floor(b);

Empty set (0.01 sec)

MariaDB [test]> select a, floor(b)*2 from tt group by a, floor(b);

ERROR 1055 (42000): 'test.tt.b' isn't in GROUP BY

MariaDB [test]> select a, mod(b,2) from tt group by a, mod(b,2);

Empty set (0.00 sec)

MariaDB [test]> select a, 2*mod(b,2) from tt group by a, mod(b,2);

ERROR 1055 (42000): 'test.tt.b' isn't in GROUP BY

...