MySQL dayofmonth()函數
DAYOFMONTH(date)
返回日期的月中的天，範圍為0〜31。
mysql> SELECT DAYOFMONTH('1998-02-03');
+---------------------------------------------------------+
| DAYOFMONTH('1998-02-03') |
+---------------------------------------------------------+
| 3 |
+---------------------------------------------------------+
1 row in set (0.00 sec)
