MySQL中ADDDATE()函数的使用教程
ADDDATE(date,INTERVALexprunit),ADDDATE(expr,days)
当被调用的第二个参数的区间形式，ADDDATE()是DATE_ADD()的同义词。相关功能SUBDATE()是DATE_SUB()的代名词。对于区间上的单元参数的详细信息，请参阅DATE_ADD()的说明。
mysql>SELECTDATE_ADD('1998-01-02',INTERVAL31DAY);
+---------------------------------------------------------+
|DATE_ADD('1998-01-02',INTERVAL31DAY)|
+---------------------------------------------------------+
|1998-02-02|
+---------------------------------------------------------+
1rowinset(0.00sec)
mysql>SELECTADDDATE('1998-01-02',INTERVAL31DAY);
+---------------------------------------------------------+
|ADDDATE('1998-01-02',INTERVAL31DAY)|
+---------------------------------------------------------+
|1998-02-02|
+---------------------------------------------------------+
1rowinset(0.00sec)
当被调用的第二个参数的形式，MySQL的把它作为一个整数天数添加到expr。
mysql>SELECTADDDATE('1998-01-02',31);
+---------------------------------------------------------+
|DATE_ADD('1998-01-02',INTERVAL31DAY)|
+---------------------------------------------------------+
|1998-02-02|
+---------------------------------------------------------+
1rowinset(0.00sec)