SQLServer和Oracle是大家经常用到的数据库，在此感谢作者总结出这些常用函数以供大家参考。

数学函数：

1.绝对值

S:SELECT abs(-1) value

O:SELECT abs(-1) value from dual

2.取整(大)

S:SELECT ceiling(-1.001) value

O:SELECT ceil(-1.001) value from dual

3.取整(小)

S:SELECT floor(-1.001) value

O:SELECT floor(-1.001) value from dual

4.取整(截取)

S:SELECT cast(-1.002 as int) value

O:SELECT trunc(-1.002) value from dual

5.四舍五入

S:SELECT round(1.23456,4) value 1.23460

O:SELECT round(1.23456,4) value from dual 1.2346

6.e为底的幂

S:SELECT Exp(1) value 2.7182818284590451

O:SELECT Exp(1) value from dual 2.71828182

7.取e为底的对数

S:SELECT log(2.7182818284590451) value 1

O:SELECT ln(2.7182818284590451) value from dual; 1

8.取10为底对数

S:SELECT log10(10) value 1

O:SELECT log(10,10) value from dual; 1

9.取平方

S:SELECT SQUARE(4) value 16

O:SELECT power(4,2) value from dual 16

10.取平方根

S:SELECT SQRT(4) value 2

O:SELECT SQRT(4) value from dual 2

11.求任意数为底的幂

S:SELECT power(3,4) value 81

O:SELECT power(3,4) value from dual 81

12.取随机数

S:SELECT rand() value

O:SELECT sys.dbms_random.value(0,1) value from dual;

13.取符号

S:SELECT sign(-8) value -1

O:SELECT sign(-8) value from dual -1

14.圆周率

S:SELECT PI() value 3.1415926535897931

O:不知道

15.sin,cos,tan 参数都以弧度为单位

例如：SELECT sin(PI()/2) value 得到1(SQLServer)

16.Asin,Acos,Atan,Atan2 返回弧度

17.弧度角度互换(SQLServer，Oracle不知道)

DEGREES：弧度-〉角度

RADIANS：角度-〉弧度

数值间比较：

18. 求集合最大值

S:SELECT max(value) value from

(SELECT 1 value

union

SELECT -2 value

union

SELECT 4 value

union

SELECT 3 value)a

O:SELECT greatest(1,-2,4,3) value from dual

19. 求集合最小值

S:SELE