数字运算符和函数

ceil 向上取整/进一取整
mysql> select ceil(3.01);
+------------+
| ceil(3.01) |
+------------+
|          4 |
+------------+
1 row in set (0.40 sec)


#取舍一取整，向下取整
mysql> select floor(3.99);
+-------------+
| floor(3.99) |
+-------------+
|           3 |
+-------------+
1 row in set (0.00 sec)


#整数除法
mysql> select 3/4;
+--------+
| 3/4    |
+--------+
| 0.7500 |
+--------+
1 row in set (0.00 sec)


#div
mysql> select 3 div 4;
+---------+
| 3 div 4 |
+---------+
|       0 |
+---------+
1 row in set (0.00 sec)


#取模/取余数，均为同一个概念
mysql> select 5.3 mod 3;
+-----------+
| 5.3 mod 3 |
+-----------+
|       2.3 |
+-----------+
1 row in set (0.00 sec)


#power 幂运算，2个3次方
mysql> select power(2,3);
+------------+
| power(2,3) |
+------------+
|          8 |
+------------+
1 row in set (0.07 sec)


#四舍五入
mysql> select round(3.6523,2);   //保留2位小数点
+-----------------+
| round(3.6523,2) |
+-----------------+
|            3.65 |
+-----------------+
1 row in set (0.00 sec)

mysql> select round(3.6523,1);   //保留1位小数点
+-----------------+
| round(3.6523,1) |
+-----------------+
|             3.7 |
+-----------------+
1 row in set (0.00 sec)


#数字截取，仅仅是对数字的截取，用途较少
mysql> select truncate(123.6523,2);
+----------------------+
| truncate(123.6523,2) |
+----------------------+
|               123.65 |
+----------------------+
1 row in set (0.00 sec)

mysql> select truncate(123.652,1);
+---------------------+
| truncate(123.652,1) |
+---------------------+
|               123.6 |
+---------------------+
1 row in set (0.00 sec)

mysql> select truncate(123.652,0);
+---------------------+
| truncate(123.652,0) |
+---------------------+
|                 123 |
+---------------------+
1 row in set (0.00 sec)