借助以下 MySQL 查询，我们可以获得上个月的最后一天 -

mysql> SELECT LAST_DAY(now() - INTERVAL 1 MONTH) AS 'LAST DAY OF PREVIOUS MONTH';

+----------------------------+
| LAST DAY OF PREVIOUS MONTH |
+----------------------------+
| 2017-09-30                 |
+----------------------------+
1 row in set (0.00 sec)