[导入]Oracle常用函数:DateDiff()

/*
--功能:将字符串转为年月日格式,删除时分秒.
--来源:http://jorkin.reallydo.com/article.asp?id=529
--参数:
Datechar Varchar2
--Oracle9i测试通过
*/
Create Or Replace Function CDate(Datechar In Varchar2) Return Date Is
ReallyDo Date;
Begin
Select to_date(to_char(to_date(to_char(Datechar), 'YYYY-MM-DD HH24:MI:SS'),
'YYYY-MM-DD'),
'YYYY-MM-DD')
Into ReallyDo
From Dual;
Return(ReallyDo);
End CDate;
/*
--功能:将字符串转为年月日时分秒格式.
--来源:http://jorkin.reallydo.com/article.asp?id=529
--参数:
Datechar Varchar2
--Oracle9i测试通过
*/
Create Or Replace Function CDateTime(Datechar In Varchar2) Return Date Is
ReallyDo Date;
Begin
Select to_date(to_char(to_date(to_char(Datechar), 'YYYY-MM-DD HH24:MI:SS'),
'YYYY-MM-DD HH24:MI:SS'),
'YYYY-MM-DD HH24:MI:SS')
Into ReallyDo
From Dual;
Return(ReallyDo);
End CDateTime;
/*
--功能:类似MSSQL的日期比较函数
--来源:http://jorkin.reallydo.com/article.asp?id=529
--更新时间:20080721
--参数:
Datepart Varchar2 -- 比较年?月?日?
StartDate Varchar2 -- 起始日期
EndDate Varchar2 -- 结束日期
--Oracle9i测试通过
*/
Create Or Replace Function Datediff
(
Datepart In Varchar2,
StartDate In Varchar2,
EndDate In Varchar2
) Return Number Is
ReallyDo Numeric;
Begin
Select Case Upper(Datepart)
When 'YYYY' Then
Trunc(Extract(Year From CDate(EndDate)) -
Extract(Year From CDate(StartDate)))
When 'M' Then
Datediff('YYYY', StartDate, EndDate) * 12 +
(Extract(Month From CDate(EndDate)) -
Extract(Month From CDate(StartDate)))
When 'D' Then
Trunc(CDate(EndDate) - CDate(StartDate))
When 'H' Then
Datediff('D', StartDate, EndDate) * 24 +
(to_Number(to_char(CDateTime(EndDate), 'HH24')) -
to_Number(to_char(CDateTime(StartDate), 'HH24')))
When 'N' Then
Datediff('D', StartDate, EndDate) * 24 * 60 +
(to_Number(to_char(CDateTime(EndDate), 'MI')) -
to_Number(to_char(CDateTime(StartDate), 'MI')))
When 'S' Then
Datediff('D', StartDate, EndDate) * 24 * 60 * 60 +
(to_Number(to_char(CDateTime(EndDate), 'SS')) -
to_Number(to_char(CDateTime(StartDate), 'SS')))
Else
-29252888
End
Into ReallyDo
From Dual;
Return(ReallyDo);
End Datediff;

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