oraclesql语句⽐较时间,SQL语句⽐较时间-SQL常⽤函数与
ORACLE⽐较
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
----------三⾓函数相关
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
oracle四舍五入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
--------字符串函数
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
23.⼦串位置 --返回3
S:select CHARINDEX('s','sdsq',2) value
O:select INSTR('sdsq','s',2) value from dual
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可以通过第四个参数控制出现次数select INSTR('sdsfasdqe','sd',1,2) value from dual 返回6 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
O:SELECT Replace('abcdef', 'bcd', 'ijklmn') value from dual 26.⼦串全部替换
S:Replace
O:select Translate('fasdbfasegas','fa','我' ) value from dual
27.长度
S:len,datalength
O:length
28.⼤⼩写转换 lower,upper
29.单词⾸字母⼤写
S：没发现
O:select INITCAP('abcd dsaf df') value from dual
30.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
31.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
32.删除空格
S:ltrim,rtrim
O:ltrim,rtrim,trim
33. 重复字符串
S:select REPLICATE('abcd',2) value
O：没发现
34.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
--------------⽇期函数
35.系统时间
S:select getdate() value
O:select sysdate value from dual
36.前后⼏⽇
直接与整数相加减
37.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
38.求时间
S:select convert(char(8),getdate(),108) value
O:select to_char(sysdate,'hh24:mm:ss') value from dual
39.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)
----------------------------------------------
40.当⽉最后⼀天
S：不知道
O:select LAST_DAY(sysdate) value from dual
41.本星期的某⼀天(⽐如星期⽇)
S：不知道
O:SELECT Next_day(sysdate,7) vaule FROM DUAL;
42.字符串转时间
S：可以直接转或者select cast('2004-09-08'as datetime) value
O:SELECT To_date('2004-01-05 22:09:38','yyyy-mm-dd hh24-mi-ss') vaule FROM DUAL;
43.求两⽇期某⼀部分的差(⽐如秒)
S:select datediff(ss,getdate(),getdate()+12.3) value
O：直接⽤两个⽇期相减(⽐如d1-d2=12.3)

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