常用数值函数

• abs(x)返回x的绝对值

  select abs(-1), abs(1), abs(0);
  +---------+--------+--------+
  | abs(-1) | abs(1) | abs(0) |
  +---------+--------+--------+
  |       1 |      1 |      0 |
  +---------+--------+--------+

• ceil(x)返回大于x的最小整数值

  select ceil(-5), ceil(5), ceil(-5.1), ceil(5.1);
  +----------+---------+------------+-----------+
  | ceil(-5) | ceil(5) | ceil(-5.1) | ceil(5.1) |
  +----------+---------+------------+-----------+
  |       -5 |       5 |         -5 |         6 |
  +----------+---------+------------+-----------+
  

• floor(x)返回小于x的最大整数值

  select floor(-5), floor(5), floor(5.1), floor(-5.1);
  +-----------+----------+------------+-------------+
  | floor(-5) | floor(5) | floor(5.1) | floor(-5.1) |
  +-----------+----------+------------+-------------+
  |        -5 |        5 |          5 |          -6 |
  +-----------+----------+------------+-------------+
  

• MOD(x,y)返回x/y的模。模数和被模数任意一个为null，结果就为null。

  select mod(10,2), mod(5,2), mod(2.5, 0.3), mod(null, 1), mod(1, null);
  +-----------+----------+---------------+--------------+--------------+
  | mod(10,2) | mod(5,2) | mod(2.5, 0.3) | mod(null, 1) | mod(1, null) |
  +-----------+----------+---------------+--------------+--------------+
  |         0 |        1 |           0.1 |         NULL |         NULL |
  +-----------+----------+---------------+--------------+--------------+
  

• rand()返回0-1的随机值 ```sql select rand(); +—————————-+ | rand() | +—————————-+ | 0.947478930416963 | +—————————-+

select ceil(rand()100); +—————————+ | ceil(rand()100) | +—————————+ | 80 | +—————————+

- 
`round(x, y)`返回参数x的四舍五入有y位小数的值
```sql
select round(5.333, 2), round(5.335, 2), round(5.2), round(null), round(1, null);
+-----------------+-----------------+------------+-------------+----------------+
| round(5.333, 2) | round(5.335, 2) | round(5.2) | round(null) | round(1, null) |
+-----------------+-----------------+------------+-------------+----------------+
|            5.33 |            5.34 |          5 |        NULL |           NULL |
+-----------------+-----------------+------------+-------------+----------------+

• truncate(x, y)返回数字x截断为y位小数的结果。与round的区别，仅仅截断，没有四舍五入。

  select truncate(5.3333, 2), truncate(5.335, 2), truncate(null, 2), truncate(5.33, null);
  +---------------------+--------------------+-------------------+----------------------+
  | truncate(5.3333, 2) | truncate(5.335, 2) | truncate(null, 2) | truncate(5.33, null) |
  +---------------------+--------------------+-------------------+----------------------+
  |                5.33 |               5.33 |              NULL |                 NULL |