简单总结 MySQL数学函数

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 |

+----------+

3. SQRT(x): 返回x的平方根，要求（x为非负数，返回NULL）

mysql> select SQRT(49), SQRT(0), SQRT(-49);

+----------+---------+-----------+

| SQRT(49) | SQRT(0) | SQRT(-49) |

+----------+---------+-----------+

|        7 |       0 |      NULL |

+----------+---------+-----------+

4. MOD(x,y): 求余函数，返回x被y除后的余数；对于带有小数部分的数据值也起作用，它返回除法运算后的精确余数。

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１

mysql> 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 |

+--------------+--------------------+-----------+-------------------+--------------------+--------------------+-------------------+

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