OracleMysqlSqlServer函数区别

O:select CONCAT('11','22')||33 value from dual
23.子串位置 --返回3
S:select CHARINDEX('s','sdsq',2) value
O:select INSTR('sdsq','s',2) value from dual
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
24.求子串
S:select substring('abcd',2,2) value
O:select substr('abcd',2,2) value from dual
25.子串代替 返回aijklmnef
S:SELECT STUFF('abcdef', 2, 3, 'ijklmn') value
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
--Mysql
select cast('123' as signed integer); --123
select cast(33 as char(2)); --33；
select to_days('2000-01-01'); --730485
--SqlServer
select cast('123' as decimal(30,2)); --123.00
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
select current_date(); --日期
--SqlServer
select getdate(); --日期时间
select datediff(day,'2010-01-01',cast(getdate() as varchar(10)));--日期相差天数
4.Decode函数
23.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可以通过第四霾问刂瞥鱿执问?BR> select INSTR('sdsfasdqe','sd',1,2) value from dual 返回6
S:len,datalength
O:length
28.大小写转换 lower,upper
29.单词首字母大写
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
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
--------数值间比较
21.求字符序号
S:select ascii('a') value
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
8.把多行转换成一合并列
--Oracle
select wm_concat(列名) from dual; --多行记录转换成一列之间用,分割
--Mysql/SqlServer
select group_concat(列名);
SQLServer和Oracle的常用函数对比
1.绝对值
select cast(33 as char(2)); --33；
select convert(varchar(12) , getdate(), 120)
2.四舍五入函数区别
--Oracle
select round(12.86*10)/10 from dual; --12.9
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
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）
--Mysql
select format(12.89,1); --12.9
--SqlServer
select round(12.89,1); --12.9
Hale Waihona Puke 3.日期时间函数 --Oracle
select sysdate from dual; --日期时间
--Mysql
select sysdate(); --日期时间
where rownum <= 20
)
-- 10 = (currentPage-1) * pageSize
where rn > 10;
-- Oralce 分页算法二
-- 20 = (currentPage-1) * pageSize + pageSize
--Oracle
select decode(sign(12),1,1,0,0,-1) from dual;--1
--Mysql/SqlServer
select case when sign(12)=1 then 1 when sign(12)=0 then 0 else -1 end;--1
-- Oracle 分页算法一
select * from (
select page.*,rownum rn from (select * from help) page
-- 20 = (currentPage-1) * pageSize + pageSize
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
O:SELECT Replace('abcdef', 'bcd', 'ijklmn') value from dual
26.子串全部替换
S:没发现
O:select Translate('fasdbfasegas','fa','我' ) value from dual
27.长度
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
select concat('1','2'); --12
--Mysql
select concat('1','2'); --12
--SqlServer
select '1'+'2'; --12
7.记录限制函数
--Oracle
select 1 from dual where rownum <= 10;
Oracle/Mysql/SqlServer函数区别