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。
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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 | 1.830487721712412452 | +--------------+--------------------+-----------+-------------------+--------------------+--------------------+-------------------+
