STR_TO_DATE MySQL 5.7

gistfile1.txt

mysql2 mysql> select str_to_date('9','%m');
+-----------------------+
| str_to_date('9','%m') |
+-----------------------+
| NULL                  |
+-----------------------+
1 row in set, 1 warning (0.00 sec)

mysql2 mysql> show variables like 'sql_mode'\G
*************************** 1. row ***************************
Variable_name: sql_mode
        Value: ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
1 row in set (0.00 sec)

mysql2 mysql> set sql_mode='';
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql2 mysql> select str_to_date('9','%m');
+-----------------------+
| str_to_date('9','%m') |
+-----------------------+
| 0000-09-00            |
+-----------------------+
1 row in set (0.00 sec)


Check the manual: http://dev.mysql.com/doc/refman/5.7/en/date-and-time-functions.html#function_str-to-date