MySQL函数学习笔记一：数学函数_MySQL-mysql教程-PHP中文网

1. ABS(x): 返回x的绝对值

mysql> select ABS(1), ABS(-1), ABS(0);
-------- --------- --------
| ABS(1) | ABS(-1) | ABS(0) |
-------- --------- --------
| 1 | 1 | 0 |
-------- --------- --------

2. PI(): 返回圆周率

mysql> select PI();
----------
| PI() |
----------
| 3.141593 |
----------

mysql> select MOD(31,8), MOD(21,-8), MOD(-7,2), MOD(-7,-2), MOD(45.5,6);
----------- ------------ ----------- ------------ -------------
| MOD(31,8) | MOD(21,-8) | MOD(-7,2) | MOD(-7,-2) | MOD(45.5,6) |
----------- ------------ ----------- ------------ -------------
| 7 | 5 | -1 | -1 | 3.5 |
----------- ------------ ----------- ------------ -------------

5. CEIL(X): 返回不小X的最小整数值，返回值转为一个BIGINT.

mysql> select CEIL(-3.35), CEIL(3.35);
------------- ------------
| CEIL(-3.35) | CEIL(3.35) |
------------- ------------
| -3 | 4 |
------------- ------------

6. CEILING(X): 同CEIL(X)

mysql> select CEILING(-3.35), CEILING(3.35);
---------------- ---------------
| CEILING(-3.35) | CEILING(3.35) |
---------------- ---------------
| -3 | 4 |
---------------- ---------------

7. FLOOR(X):返回不大于X的最大整数值，返回值转为一个BIGINT.

mysql> select FLOOR(-3.35), FLOOR(3.35);
-------------- -------------
| FLOOR(-3.35) | FLOOR(3.35) |
-------------- -------------
| -4 | 3 |
-------------- -------------

8. RAND()和RAND(X)

RAND(X) 返回一个随机浮点值，范围在０～１之间，X为整数，它被称作种子值，用来产生重复序列。即当Ｘ值相同时，产生的随机数也相同；

mysql> select RAND(10), RAND(10), RAND(2), RAND(-2);
-------------------- -------------------- -------------------- --------------------
| RAND(10) | RAND(10) | RAND(2) | RAND(-2) |
-------------------- -------------------- -------------------- --------------------
| 0.6570515219653505 | 0.6570515219653505 | 0.6555866465490187 | 0.6548542125661431 |
-------------------- -------------------- -------------------- --------------------

RAND(): 不带参数的RAND()每次产生不同０～１之间的随机数

mysql> SELECT RAND(), RAND(), RAND();
-------------------- -------------------- ---------------------
| RAND() | RAND() | RAND() |
-------------------- -------------------- ---------------------
| 0.6931893636409094 | 0.5147262984092592 | 0.49406343185721285 |
-------------------- -------------------- ---------------------

9. ROUND(X)和ROUND(X,Y): 四舍五入函数，对Ｘ值按照Ｙ进行四舍五入，Ｙ可以省略，默认值为０;若Ｙ不为０，则保留小数点后面指定Ｙ位。

mysql> select ROUND(-1.14), ROUND(-1.9), ROUND(1.14), ROUND(1.9);
-------------- ------------- ------------- ------------
| ROUND(-1.14) | ROUND(-1.9) | ROUND(1.14) | ROUND(1.9) |
-------------- ------------- ------------- ------------
| -1 | -2 | 1 | 2 |
-------------- ------------- ------------- ------------

mysql> select ROUND(1.38,1), ROUND(1.38,0), ROUND(232.38,-1), ROUND(232.38,-2);
--------------- --------------- ------------------ ------------------
| ROUND(1.38,1) | ROUND(1.38,0) | ROUND(232.38,-1) | ROUND(232.38,-2) |
--------------- --------------- ------------------ ------------------
| 1.4 | 1 | 230 | 200 |
--------------- --------------- ------------------ ------------------

10. TRUNCATE(X,Y): 与ROUND(X,Y)功能类似，但不进行四舍五入，只进行截取。

mysql> select TRUNCATE(1.33,1), TRUNCATE(1.99,1), TRUNCATE(1.99,0), TRUNCATE(19.99,-1);
------------------ ------------------ ------------------ --------------------
| TRUNCATE(1.33,1) | TRUNCATE(1.99,1) | TRUNCATE(1.99,0) | TRUNCATE(19.99,-1) |
------------------ ------------------ ------------------ --------------------
| 1.3 | 1.9 | 1 | 10 |
------------------ ------------------ ------------------ --------------------

11. SIGN(X): 返回参数Ｘ的符号，Ｘ的值为负、零或正数时返回结果依次为－１，０或１mysql> select SIGN(-21), SIGN(-0),SIGN(0), SIGN(0.0), SIGN(21);
----------- ---------- --------- ----------- ----------
| SIGN(-21) | SIGN(-0) | SIGN(0) | SIGN(0.0) | SIGN(21) |
----------- ---------- --------- ----------- ----------
| -1 | 0 | 0 | 0 | 1 |
----------- ---------- --------- ----------- ----------

12. POW(X,Y), POWER(X,Y)和EXP(X)

POW(X,Y)与POWER(X,Y)功能相同，用于返回Ｘ的Ｙ次乘方的结果值

mysql> select pow(2,2), pow(2,-2), pow(-2,2), pow(-2,-2);
---------- ----------- ----------- ------------
| pow(2,2) | pow(2,-2) | pow(-2,2) | pow(-2,-2) |
---------- ----------- ----------- ------------
| 4 | 0.25 | 4 | 0.25 |
---------- ----------- ----------- ------------

mysql> select power(2,2), power(2,-2), power(-2,2), power(-2,-2);
------------ ------------- ------------- --------------
| power(2,2) | power(2,-2) | power(-2,2) | power(-2,-2) |
------------ ------------- ------------- --------------
| 4 | 0.25 | 4 | 0.25 |
------------ ------------- ------------- --------------

EXP(X): 返回e的Ｘ乘方后的值:

mysql> select EXP(3), EXP(0), EXP(-3);
------------------- -------- ---------------------
| EXP(3) | EXP(0) | EXP(-3) |
------------------- -------- ---------------------
| 20.08553692318767 | 1 | 0.04978706836786393 |
------------------- -------- ---------------------

13. LOG(X)和LOG10(X): 对数运算函数（Ｘ必须为正数），LOG(X)-返回Ｘ的自然对数(X相对于基数e的对数)　LOG10(X)-返回x的基数为10的对数：

mysql> select LOG(-3), LOG(0), LOG(3), LOG10(-100), LOG10(0), LOG10(100);
--------- -------- -------------------- ------------- ---------- ------------
| LOG(-3) | LOG(0) | LOG(3) | LOG10(-100) | LOG10(0) | LOG10(100) |
--------- -------- -------------------- ------------- ---------- ------------
| NULL | NULL | 1.0986122886681098 | NULL | NULL | 2 |
--------- -------- -------------------- ------------- ---------- ------------

14. RADIANS(X) 和 DEGREES(X): 角度与弧度转换函数

mysql> select RADIANS(90), RADIANS(180), DEGREES(PI()), DEGREES(PI()/2);
-------------------- ------------------- --------------- -----------------
| RADIANS(90) | RADIANS(180) | DEGREES(PI()) | DEGREES(PI()/2) |
-------------------- ------------------- --------------- -----------------
| 1.5707963267948966 | 3.141592653589793 | 180 | 90 |
-------------------- ------------------- --------------- -----------------

15. SIN(X), ASIN(X), COS(X), ACOS(X), TAN(X), ATAN(X), COT(X)

SIN(X): 正弦函数，其中Ｘ为弧度值

ASIN(X): 反正弦函数　其中Ｘ必须在－１到１之间

COS(X): 余弦函数，其中Ｘ为弧度值

ACOS(X): 反余弦函数　其中Ｘ必须在－１到１之间

TAN(X): 正切函数，其中Ｘ为弧度值

ATAN(X): 反正切函数，ATAN(X)与TAN(X)互为反函数

COT(X):　余切函数，函数COT和TAN互为倒函数

mysql> select SIGN(PI()/2),ASIN(1),COS(PI()), ACOS(-1), TAN(PI()/4), ATAN(1), COT(0.5);
-------------- -------------------- ----------- ------------------- -------------------- -------------------- -------------------
| SIGN(PI()/2) | ASIN(1) | COS(PI()) | ACOS(-1) | TAN(PI()/4) | ATAN(1) | COT(0.5) |
-------------- -------------------- ----------- ------------------- -------------------- -------------------- -------------------
| 1 | 1.5707963267948966 | -1 | 3.141592653589793 | 0.9999999999999999 | 0.7853981633974483 | 1.830487721712452 |
-------------- -------------------- ----------- ------------------- -------------------- -------------------- -------------------