问题
I'm working on a data warehouse project and would like to know how to (preferably in a Derived Column component in a Data flow) strip the date piece off of a SQL datetime record.
Once I have the datetime converted to just a time I am going to do a lookup on the time to find the related time record in a time dimension table.
Can someone give me a simple function to accomplish this inside a derived column transform?
Example: Transform a datetime such as "12/02/2008 11:32:21 AM" into simply "11:32:21 AM".
回答1:
I would just do a cast to DT_DBTIME type (using Derived Column transform, or Convert type transform). DT_DBTIME contains just (hours, minutes, seconds) part of the date/time, so you'll get rid of the date part.
回答2:
Actually if you reverse the first 2 expressions like this: (DT_DBDATE)(DT_DATE)GETDATE()
instead of (DT_DATE)(DT_DBDATE)GETDATE(), then you will TRUNCATE the time off the date field.
If the DT_DATE expression is before the DT_DBDATE expression, you will still have the time portion in your output, but it will be reset to all zeroes.
回答3:
If you need to do this in a variable expression Michael's solution won't work, but you can use the following expression:
(DT_DATE)(DT_DBDATE)GETDATE()
(DT_DBDATE) converts the current date and time to a date only. But the new datatype is not compatiple with SSIS's datetime. Therefore you'll have to use (DT_DATE) for converting to a compatible type.
Courtesy of this solution belongs to Russel Loski who has posted it in his blog: http://www.bidn.com/blogs/RussLoski/ssas/1458/converting-datetime-to-date-in-ssis
回答4:
Ran into this with writing a report for a scheduling app, needed the time that was stored as part of a datetime data type. I formated the datetime as 0 which gives you this mon dd yyyy hh:miAM (or PM), and just did a substring of that which returned the time only in an AM/PM format.
Example below.
DECLARE @S DATETIME = GETDATE()
SELECT SUBSTRING(CONVERT(NVARCHAR(30), @S , 0) , 13 , 10) AS ApptTime
, CONVERT(NVARCHAR(30), @S , 0) AS ApptDate
回答5:
I personally use a series of functions for this. E.g.:
ALTER FUNCTION [dbo].[TIMEVALUE]
(
@Datetime datetime
)
RETURNS datetime
AS
BEGIN
RETURN (@Datetime - CAST(ROUND(CAST(@Datetime AS float), 0, 1) AS datetime))
END
I'd love to claim all the credit but it should really go to this guy.
来源：https://stackoverflow.com/questions/844029/how-do-i-strip-the-date-off-of-a-datetime-string-in-sql-ssis