Mysql学习MySQL笔记之数学函数详解

发布时间：2020-12-12 01:12:17 所属栏目：MySql教程来源：网络整理

导读：《Mysql学习MySQL笔记之数学函数详解》要点：本文介绍了Mysql学习MySQL笔记之数学函数详解，希望对您有用。如果有疑问，可以联系我们。 MYSQL必读绝对值函数ABS(x)和圆周率函数PI() 代码如下: mysql SELECT ABS(0.5),ABS(-0.5),PI(); +----------+--------

《Mysql学习MySQL笔记之数学函数详解》要点：
本文介绍了Mysql学习MySQL笔记之数学函数详解，希望对您有用。如果有疑问，可以联系我们。

MYSQL必读绝对值函数ABS(x)和圆周率函数PI()

代码如下:
mysql> SELECT ABS(0.5),ABS(-0.5),PI();
+----------+-----------+----------+
| ABS(0.5) | ABS(-0.5) | PI()???? |
+----------+-----------+----------+
|????? 0.5 |?????? 0.5 | 3.141593 |
+----------+-----------+----------+
?row in set (0.00 sec)

MYSQL必读平方根函数SQRT(x)和求余函数MOD(x,y)

代码如下:
mysql> SELECT SQRT(16),SQRT(3),MOD(13,4);
+----------+--------------------+-----------+
| SQRT(16) | SQRT(3)??????????? | MOD(13,4) |
+----------+--------------------+-----------+
|??????? 4 | 1.7320508075688772 |???????? 1 |
+----------+--------------------+-----------+
?row in set (0.00 sec)

MYSQL必读取整函数CEIL(x)、CEILING(x)和FLOOR(x)

代码如下:
mysql> SELECT CEIL(2.3),CEIL(-2.3),CEILING(2.3),CEILING(-2.3);
+-----------+------------+--------------+---------------+
| CEIL(2.3) | CEIL(-2.3) | CEILING(2.3) | CEILING(-2.3) |
+-----------+------------+--------------+---------------+
|???????? 3 |???????? -2 |??????????? 3 |??????????? -2 |
+-----------+------------+--------------+---------------+
?row in set (0.00 sec)

MYSQL必读mysql> SELECT FLOOR(2.3),FLOOR(-2.3);
+------------+-------------+
| FLOOR(2.3) | FLOOR(-2.3) |
+------------+-------------+
|????????? 2 |????????? -3 |
+------------+-------------+
?row in set (0.00 sec)

CEIL(x)和CEILING(x)返回大于或等于x的最小整数

MYSQL必读FLOOR(x)返回小于或等于x的最大整数

MYSQL必读随机数函数RAND()和RAND(x)

代码如下:
mysql> SELECT RAND(),RAND(2),RAND(2);
+--------------------+--------------------+--------------------+
| RAND()???????????? | RAND(2)??????????? | RAND(2)??????????? |
+--------------------+--------------------+--------------------+
| 0.8269294489425881 | 0.6555866465490187 | 0.6555866465490187 |
+--------------------+--------------------+--------------------+
?row in set (0.00 sec)

RAND()和RAND(x)这两个函数丢失返回0～1的随机数

MYSQL必读区别在于,RAND()返回的数是完全随机的,而RAND(x)在x相同时返回的值相同

MYSQL必读四舍五入函数ROUND(x)、ROUND(x,y)和TRUNCATE(x,y)

代码如下:
mysql> SELECT ROUND(2.3),ROUND(2.5),ROUND(2.53,1),ROUND(2.55,1);
+------------+------------+---------------+---------------+
| ROUND(2.3) | ROUND(2.5) | ROUND(2.53,1) | ROUND(2.55,1) |
+------------+------------+---------------+---------------+
|????????? 2 |????????? 3 |?????????? 2.5 |?????????? 2.6 |
+------------+------------+---------------+---------------+
?row in set (0.00 sec)

ROUND(x)返回离x最近的整数,也就是对x进行四舍五入处理

MYSQL必读ROUND(x,y)返回x保留到小数点后y位的值,在截取时进行四舍五入处理

代码如下:
mysql> SELECT TRUNCATE(2.53,TRUNCATE(2.55,1);
+------------------+------------------+
| TRUNCATE(2.53,1) | TRUNCATE(2.55,1) |
+------------------+------------------+
|????????????? 2.5 |????????????? 2.5 |
+------------------+------------------+
?row in set (0.00 sec)

TRUNCATE(x,不进行四舍五入操作

MYSQL必读符号函数SIGN(x)

代码如下:
mysql> SELECT SIGN(-2),SIGN(0),SIGN(2);
+----------+---------+---------+
| SIGN(-2) | SIGN(0) | SIGN(2) |
+----------+---------+---------+
|?????? -1 |?????? 0 |?????? 1 |
+----------+---------+---------+
?row in set (0.00 sec)

SIGN(x)返回x的符号,-1为负数,0不变,1为整数

MYSQL必读
幂运算函数POW(x,y)、POWER(x,y)

代码如下:
mysql> SELECT POW(3,2),POWER(3,2);
+----------+------------+
| POW(3,2) | POWER(3,2) |
+----------+------------+
|??????? 9 |????????? 9 |
+----------+------------+
?row in set (0.00 sec)

（编辑：李大同）

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