Vertica的这些事（二）——SQL-Server、Oracle、MySQL和Vertica数据库常用函数对比

SQL Server、Oracle、MySQL和Vertica数据库常用函数对比
Vertica数据库是HP公司新收购的用于BI方面的数据库。

1. 绝对值

S:select abs(-1) value

O:select abs(-1) value from dual

M:select abs(-1) value from dual

V:select abs(-1)

2. 向上取整

S:select ceiling(-1.001) value

O:select ceil(-1.001) value from dual

M:select ceil(-1.001) value from dual

V:select ceil(-1.001)

3. 向下取整

S:select floor(-1.001) value

O:select floor(-1.001) value from dual

M:select floor(-1.001) value from dual

V:select floor(-1.001)

4. 取整（截取）

S:select cast(-1.002 as int) value

O:select trunc(-1.002) value from dual

V:select trunc(-1.002)

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

M:select round(1.23456,4) value from dual 1.2346

V:select round(1.23456,4.0)

6. e为底的幂

S:select Exp(1) value 2.71828182845905

O:select Exp(1) value from dual 2.71828182

M:select Exp(1) value from dual 2.718281828459045

V:select Exp(1.0) 2.71828182845905

7. 取e为底的对数

S:select log(2.7182818284590451) value 1

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

M:select ln(2.7182818284590451) value from dual; 1

V: select ln(2.7182818284590451) 1

8. 取10为底对数

S:select log10(10) value 1

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

M:select log(10,10) value from dual; 1

M: select log(10,10) 1

9. 取平方

S:select SQUARE(4) value 16

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

M:select power(4,2) value from dual 16

V:select power(4,2) 16

10. 取平方根

S:select SQRT(4) value 2

O:select SQRT(4) value from dual 2

M:select SQRT(4) value from dual 2

V:select SQRT(4) 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

M:select power(3,4) value from dual 81

V:select power(3,4) 81

12. 取随机数

S:select rand() value

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

M:select rand() value from dual;

V:select random()

13. 取符号

S:select sign(-8) value -1

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

M:select sign(-8) value from dual -1

V:select sign(-8) -1

14. 圆周率

S:SELECT PI() value 3.14159265358979

O: SELECT ACOS(-1) FROM DUAL;

M: SELECT ACOS(-1) FROM DUAL; 3.141592653589793

V: SELECT PI() 3.14159265358979

数值间比较
15. 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

M:select greatest(1,-2,4,3) value from dual

V:select greatest(1,-2,4,3)

16. 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

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

V:select least(1,-2,4,3)

17. 如何处理null值(F2中的null以10代替)

Create table tbl (f1 varchar(10),f2 int);

Insert into tbl(f1,f2) values(‘aa’,null);

Insert into tbl(f1,f2) values(‘bb’,7);

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

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

M:select F1,ifnull(F2,10) value from Tbl

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

18. 求字符ascii码

S:select ascii('a') value

O:select ascii('a') value from dual

M:select ascii('a') value from dual

V:select ascii('a')

19. 从ascii码求字符

S:select char(97) value

O:select chr(97) value from dual

M:select char(97) value from dual

V:select chr(97)

20. 连接字符串

S:select '11'+'22'+'33' value

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

M:select concat('11','22','33') value

V:select '11'||'22'||'33'

21. 子串位置 --返回3

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

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

M:select LOCATE('s','sdsq',2) value from dual

V:select INSTR('sdsq','s',2)

22. 求子串

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

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

M:select substr('abcd',2,2) value from dual

V:select substr('abcd',2,2)

23. 子串代替 返回aijklmnef

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

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

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

V:SELECT Replace('abcdef', 'bcd', 'ijklmn')

24. 字符串长度

S:len,datalength

O: select length('aaa') value from dual

M: select length('aaa') value from dual

V: select length('aaa '::CHAR(10))

Select length('aaa '::varchar(10))

select length('aaa')

25. 大小写转换 lower,upper
26. 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

M:select LPAD('abcd',14, ' ') value from dual

V:select LPAD('abcd',14, ' ') value from dual

27. 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

M:select RPAD('abcd',14, ' ') value from dual

V:select RPAD('abcd',14, ' ') value from dual

28. 删除空格

S:ltrim,rtrim

O:ltrim,rtrim,trim

M:ltrim,rtrim,trim

V:ltrim,rtrim,trim

日期函数
29. 系统时间

S:select getdate() value

O:select sysdate value from dual

M:select now() value from dual

V:select sysdate()

select getdate()

select now() 会显示时区

30. 前后几日

S:直接与整数相加减

O:直接与整数相加减

M: select now()+interval 1 day value from dual

V:直接与整数相加减

31. 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

M:select DATE_FORMAT(NOW(),'%Y-%m-%d') value from dual;

V:select to_char(sysdate(),'YYYY-MM-DD')

32. 求时间

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

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

M:select DATE_FORMAT(NOW(),'%T') value from dual

V:select to_char(sysdate,'hh24:mi:ss')

33. 取日期时间的其他部分

S:DATEPART 和 DATENAME 函数 （第一个参数决定）

O:to_char函数 第二个参数决定

参数---------------------------------下表需要补充

year yy, yyyy

quarter qq, q (季度)

month mm, m (m O无效)

dayofyear dy, y (O表星期)

day dd, d (d O无效)

week wk, ww (wk O无效)

weekday dw (O不清楚)

Hour hh,hh12,hh24 (hh12,hh24 S无效)

minute mi, n (n O无效)

second ss, s (s O无效)

millisecond ms (O无效)

M:date_format函数 第二个参数决定

格式

描述

%a

缩写星期名

%b

缩写月名

%c

月，数值

%D

带有英文前缀的月中的天

%d

月的天，数值(00-31)

%e

月的天，数值(0-31)

%f

微秒

%H

小时 (00-23)

%h

小时 (01-12)

%I

小时 (01-12)

%i

分钟，数值(00-59)

%j

年的天 (001-366)

%k

小时 (0-23)

%l

小时 (1-12)

%M

月名

%m

月，数值(00-12)

%p

AM 或 PM

%r

时间，12-小时（hh:mm:ss AM 或 PM）

%S

秒(00-59)

%s

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