MySQL常用数值函数小结
备注:测试数据库版本为MySQL 8.0
文章目录
- 一.mod
- 二.ceil
- 三.floor
- 四.round
- 五.truncate
- 六.rand
- 七.greatest
- 八.least
这个blog我们来聊聊常见的数值函数
| 函数名 | 函数用途 |
|---|---|
| mod | 取余 |
| ceil | 向上取整 |
| floor | 向下取整 |
| round | 四舍五入 |
| truncate | 截断函数 |
| rand | 随机数 |
| greatest | 求最大值 |
| least | 求最小值 |
一.mod
mod取余函数
语法:MOD(N,M), N % M, N MOD M
mysql> select mod(10,3);
+-----------+
| mod(10,3) |
+-----------+
| 1 |
+-----------+
1 row in set (0.01 sec)
mysql> select 10%3;
+------+
| 10%3 |
+------+
| 1 |
+------+
1 row in set (0.00 sec)
mysql> select 10 mod 3;
+----------+
| 10 mod 3 |
+----------+
| 1 |
+----------+
1 row in set (0.00 sec)
二.ceil
CEIL向上取整函数
CEIL() 是CEILING()的同义词，两个都可以使用
ceil语法: ceil(X)
--正数向上取证
mysql> select ceil(1.1);
+-----------+
| ceil(1.1) |
+-----------+
| 2 |
+-----------+
1 row in set (0.01 sec)
--负数是找到比它大的整数,这个要注意
mysql> select ceil(-1.1);
+------------+
| ceil(-1.1) |
+------------+
| -1 |
+------------+
1 row in set (0.00 sec)
--对于百位向上取整，可以先除再乘
mysql> select ceil(135/100)*100;
+-------------------+
| ceil(135/100)*100 |
+-------------------+
| 200 |
+-------------------+
1 row in set (0.00 sec)
三.floor
floor语句是向下取整，与ceil相反
floor语法:FLOOR(X)
--正数向下取证
mysql> select floor(1.1);
+------------+
| floor(1.1) |
+------------+
| 1 |
+------------+
1 row in set (0.00 sec)
--负数是找到比它小的整数,这个要注意
mysql> select floor(-1.1);
+-------------+
| floor(-1.1) |
+-------------+
| -2 |
+-------------+
1 row in set (0.00 sec)
--对于百位向下取整，可以先除再乘
mysql> select floor(123/100)*100;
+--------------------+
| floor(123/100)*100 |
+--------------------+
| 100 |
+--------------------+
1 row in set (0.00 sec)
四.round
round() 四舍五入
语法:ROUND(X), ROUND(X,D)
--默认四舍五入整数
mysql> select round(1.4);
+------------+
| round(1.4) |
+------------+
| 1 |
+------------+
1 row in set (0.01 sec)
mysql> select round(1.5);
+------------+
| round(1.5) |
+------------+
| 2 |
+------------+
1 row in set (0.00 sec)
--默认四舍五入整数，负数的时候注意
mysql> select round(-1.4);
+-------------+
| round(-1.4) |
+-------------+
| -1 |
+-------------+
1 row in set (0.00 sec)
mysql> select round(-1.5);
+-------------+
| round(-1.5) |
+-------------+
| -2 |
+-------------+
1 row in set (0.00 sec)
--还可以指定保留小数的为主
mysql> select round(1.245,2);
+----------------+
| round(1.245,2) |
+----------------+
| 1.25 |
+----------------+
1 row in set (0.00 sec)
五.truncate
truncate() 截断函数
语法:TRUNCATE(X,D)
--truncate截断指定位数之后的小数，不会四舍五入
mysql> select truncate(1.4,0);
+-----------------+
| truncate(1.4,0) |
+-----------------+
| 1 |
+-----------------+
1 row in set (0.00 sec)
mysql> select truncate(1.5,0);
+-----------------+
| truncate(1.5,0) |
+-----------------+
| 1 |
+-----------------+
1 row in set (0.00 sec)
--truncate截断指定位数之后的小数，对负数也一样
mysql> select truncate(-1.4,0);
+------------------+
| truncate(-1.4,0) |
+------------------+
| -1 |
+------------------+
1 row in set (0.00 sec)
mysql> select truncate(-1.5,0);
+------------------+
| truncate(-1.5,0) |
+------------------+
| -1 |
+------------------+
1 row in set (0.00 sec)
--truncate截断指定位数之后的小数，位数可以是负数，这样就可以截断整数部分
mysql> select truncate(123,-1);
+------------------+
| truncate(123,-1) |
+------------------+
| 120 |
+------------------+
1 row in set (0.01 sec)
mysql> select truncate(123,-2);
+------------------+
| truncate(123,-2) |
+------------------+
| 100 |
+------------------+
1 row in set (0.00 sec)
六.rand
RAND() 随机数，
语法:RAND([N])
rand返回的值 0 <= v < 1.0
如果要返回区间:
7 <= R < 12 – SELECT FLOOR(7 + (RAND() * 5));
mysql> select rand();
+--------------------+
| rand() |
+--------------------+
| 0.6739231829288631 |
+--------------------+
1 row in set (0.00 sec)
mysql> select rand();
+---------------------+
| rand() |
+---------------------+
| 0.02787296476575822 |
+---------------------+
1 row in set (0.00 sec)
mysql> SELECT FLOOR(7 + (RAND() * 5));
+-------------------------+
| FLOOR(7 + (RAND() * 5)) |
+-------------------------+
| 7 |
+-------------------------+
1 row in set (0.00 sec)
mysql> SELECT FLOOR(7 + (RAND() * 5));
+-------------------------+
| FLOOR(7 + (RAND() * 5)) |
+-------------------------+
| 9 |
+-------------------------+
1 row in set (0.00 sec)
七.greatest
greatest 求最大值，如有null，则返回null
greatest语法:greatest(n1,n2,n3…)
mysql> select greatest(1,2);
+---------------+
| greatest(1,2) |
+---------------+
| 2 |
+---------------+
1 row in set (0.00 sec)
mysql> select greatest(1,2,3);
+-----------------+
| greatest(1,2,3) |
+-----------------+
| 3 |
+-----------------+
1 row in set (0.00 sec)
mysql> select greatest(1,2,3,null);
+----------------------+
| greatest(1,2,3,null) |
+----------------------+
| NULL |
+----------------------+
1 row in set (0.00 sec)
八.least
least 求最大值，如有null，则返回null
least语法:greatest(n1,n2,n3…)
mysql> select least(1,2);
+------------+
| least(1,2) |
+------------+
| 1 |
+------------+
1 row in set (0.00 sec)
mysql> select least(1,2,3);
+--------------+
| least(1,2,3) |
+--------------+
| 1 |
+--------------+
1 row in set (0.00 sec)
mysql> select least(1,2,3,null);
+-------------------+
| least(1,2,3,null) |
+-------------------+
| NULL |
+-------------------+
1 row in set (0.00 sec)