场景
财务干系的数据存储常日会用到小数，那么一样平常利用decimal类型来存储，如打算税率、利润率等，我们一样平常通过程序去打算，但是在导表等某些场景下也可以通过MySQL内置函数来实现。
语法
round(x, n) 四舍五入，保留n位小数，跟php一样一样的truncate(x, n) 保留n位小数，但是不四舍五入
利用
--如果不写小数位，那便是整数四舍五入select round(1.09821);+----------------+| round(1.09821) |+----------------+| 1 |+----------------+1 row in set (0.00 sec)select round(1.89821);+----------------+| round(1.89821) |+----------------+| 2 |+----------------+1 row in set (0.00 sec)--四舍五入select round(1.09821, 2);+-------------------+| round(1.09821, 2) |+-------------------+| 1.10 |+-------------------+1 row in set (0.00 sec)select round(1.99121, 2);+-------------------+| round(1.99121, 2) |+-------------------+| 1.99 |+-------------------+1 row in set (0.00 sec)--truncate 不会四舍五入select truncate(1.09821, 2);+----------------------+| truncate(1.09821, 2) |+----------------------+| 1.09 |+----------------------+1 row in set (0.00 sec)select truncate(1.09121, 2);+----------------------+| truncate(1.09121, 2) |+----------------------+| 1.09 |+----------------------+1 row in set (0.00 sec)
