SQLServer与Oracle常用函数实例对比汇总

一、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:没找到

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没找到)
DEGREES：弧度-〉角度
RADIANS：角度-〉弧度

二、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:select min(value) value from 

(select 1 value

union

select -2 value

union

select 4 value

union

select 3 value)a

O:select least(1,-2,4,3) value from dual

20.如何处理null值(F2中的null以10代替)

S:select F1,IsNull(F2,10) value from Tbl

O:select F1,nvl(F2,10) value from Tbl

21.求字符序号

S:select ascii(a) value

O:select ascii(a) value from dual

22.从序号求字符

S:select char(97) value

O:select chr(97) value from dual

23.连接

S:select 11+22+33 value

O:select CONCAT(11,22)||33 value from dual 

24.子串位置 --返回3

S:select CHARINDEX(s,sdsq,2) value 

O:select INSTR(sdsq,s,2) value from dual

25.模糊子串的位置 --返回2,参数去掉中间%则返回7

S:select patindex(%d%q%,sdsfasdqe) value 

O:oracle没发现，但是instr可以通过第四个参数控制出现次数

select INSTR(sdsfasdqe,sd,1,2) value from dual 返回6

26.求子串

S:select substring(abcd,2,2) value 

O:select substr(abcd,2,2) value from dual

27.子串代替 返回aijklmnef

S:SELECT STUFF(abcdef, 2, 3, ijklmn) value

O:SELECT Replace(abcdef, bcd, ijklmn) value from dual

28.子串全部替换

S:没发现

O:select Translate(fasdbfasegas,fa,我 ) value from dual

29.长度

S:len,datalength

O:length

30.大小写转换 lower,upper

31.单词首字母大写

S:没发现

O:select INITCAP(abcd dsaf df) value from dual

32.左补空格（LPAD的第一个参数为空格则同space函数）

S:select space(10)+abcd value

O:select LPAD(abcd,14) value from dual

33.右补空格（RPAD的第一个参数为空格则同space函数）

S:select abcd+space(10) value

O:select RPAD(abcd,14) value from dual

34.删除空格

S:ltrim,rtrim

O:ltrim,rtrim,trim

35. 重复字符串

S:select REPLICATE(abcd,2) value 

O:没发现

36.发音相似性比较(这两个单词返回值一样，发音相同)

S:SELECT SOUNDEX (Smith), SOUNDEX (Smythe)

O:SELECT SOUNDEX (Smith), SOUNDEX (Smythe) from dual

SQLServer中用SELECT DIFFERENCE(Smithers, Smythers) 比较soundex的差
返回0-4，4为同音，1最高

三、日期函数

37.系统时间

S:select getdate() value

O:select sysdate value from dual

38.前后几日
直接与整数相加减

39.求日期

S:select convert(char(10),getdate(),20) value

O:select trunc(sysdate) value from dual

select to_char(sysdate,yyyy-mm-dd) value from dual

40.求时间

S:select convert(char(8),getdate(),108) value

O:select to_char(sysdate,hh24:mm:ss) value from dual