模拟Oracle中的TO_CHAR()和TO_DATE

--模拟TO_DATE
CREATE FUNCTION [DBO].[TO_DATE](
@ITIME VARCHAR(30),
@IMATCH VARCHAR(30)
)RETURNS VARCHAR(30)
AS
BEGIN
DECLARE @V_DAY VARCHAR(2);
DECLARE @V_MONTH VARCHAR(2);
DECLARE @V_YEAR VARCHAR(4);

SET @V_DAY = SUBSTRING(@ITIME,1,2)
SET @V_MONTH = SUBSTRING(@ITIME,4,2)
SET @V_YEAR = SUBSTRING(@ITIME,7,4)

RETURN @V_YEAR + '-' + @V_MONTH + '-' + @V_DAY + SUBSTRING(@ITIME,11,LEN(@ITIME))
END
GO

--模拟TO_CHAR
CREATE FUNCTION [dbo].[TO_ORACHAR](
@i_Date DATETIME,
@i_Dfmt VARCHAR(25)
)RETURNS VARCHAR(25)
AS BEGIN
DECLARE @v_DateStr VARCHAR(25);
DECLARE @v_rStrFmt VARCHAR(25);

SELECT @v_DateStr = CONVERT(VARCHAR(25), @i_Date, 20);
SELECT @v_rStrFmt = UPPER(@i_Dfmt);

IF CHARINDEX('YYYY', @v_rStrFmt) > 0
SELECT @v_rStrFmt = REPLACE(@v_rStrFmt, 'YYYY', LEFT(@v_DateStr, 4));
IF CHARINDEX('MM', @v_rStrFmt) > 0
SELECT @v_rStrFmt = REPLACE(@v_rStrFmt, 'MM', SUBSTRING(@v_DateStr, 6, 2));
IF CHARINDEX('DD', @v_rStrFmt) > 0
SELECT @v_rStrFmt = REPLACE(@v_rStrFmt, 'DD', SUBSTRING(@v_DateStr, 9, 2));
IF CHARINDEX('HH24', @v_rStrFmt) > 0
SELECT @v_rStrFmt = REPLACE(@v_rStrFmt, 'HH24', SUBSTRING(@v_DateStr, 12, 2));
IF CHARINDEX('HH', @v_rStrFmt) > 0
SELECT @v_rStrFmt = REPLACE(@v_rStrFmt, 'HH', SUBSTRING(@v_DateStr,12, 2));
IF CHARINDEX('MI', @v_rStrFmt) > 0
SELECT @v_rStrFmt = REPLACE(@v_rStrFmt, 'MI', SUBSTRING(@v_DateStr,15, 2));
IF CHARINDEX('SS', @v_rStrFmt) > 0
SELECT @v_rStrFmt = REPLACE(@v_rStrFmt, 'SS', SUBSTRING(@v_DateStr,18, 2));
RETURN RTRIM(@v_rStrFmt);
END
GO