ceil() /ceiling()使用实例：
mysql> select ceiling(3.46);+---------------------------------------------------------+| ceiling(3.46) |+---------------------------------------------------------+| 4 |+---------------------------------------------------------+1 row in set (0.00 sec)mysql> select ceil(-6.43);+---------------------------------------------------------+| ceil(-6.43) |+---------------------------------------------------------+| -6 |+---------------------------------------------------------+1 row in set (0.00 sec)
注意：该函数是向上取整，返回的是大于x的最小整数值。注意负数值的情况。