NVARCHAR TO DATETIME conversion - sql

Question

I have a parameter that has a value of 14-Sep-2012 15:47:27 that I would like to update a table column with which is in 2012-08-10 05:00:00.000 format.
What would be the query needed '
#UpdateTime = '14-Sep-2012 15:47:27'
Update tbl
Set Datetimecol = CONVERT(datetime,#UpdateTime,110) ??
I am using SQL Server 2008. Thank you !

Answer 1

For the edited question, you only need to drop the 110 specification. There really isn't a specification for the format you have shown, but English installations of SQL Server will convert it.
e.g.
declare #UpdateTime datetime = '14-Sep-2012 15:47:27'
select CONVERT(datetime,#UpdateTime)
-- result
September, 14 2012 15:47:27
Assuming your month portion is at least 3 characters long, e.g. Mar, Marc, March, Sept, you can convert that very bad text datetime to a normal 3-char month format using the following
declare #updatetime nvarchar(20) = '18-Sept-2012'
declare #fixedtime nvarchar(20)
set #fixedtime = stuff(#updatetime,1,charindex('-',#updatetime),'')
set #fixedtime = Left(#updatetime,charindex('-',#updatetime))
+ stuff(#fixedtime,4,len(#fixedtime)-8,'')
-- #fixedtime contains `18-Sep-2012`
Update tbl
Set Datetimecol = #fixedtime
Yes, I deliberately left out the CAST/CONVERT in the update statement.

Answer 2

As long as your language settings are always English and your regional settings don't change, here is another approach (along with sample data of various potential formats):
DECLARE #x TABLE(y NVARCHAR(15));
INSERT #x VALUES('18-Sept-2012'),('9-May-2012'),('19-Oct-2012'),('04-March-2012');
SELECT z, CONVERT(DATETIME,z) FROM
(
SELECT SUBSTRING(y,s+1,3) + ' ' + LEFT(y,s-1) + ', ' + RIGHT(y,4) FROM
(
SELECT y, CHARINDEX('-',y) FROM #x
) AS y(y,s)
) AS z(z);
Results:
Sep 18, 2012 2012-09-18 00:00:00.000
May 9, 2012 2012-05-09 00:00:00.000
Oct 19, 2012 2012-10-19 00:00:00.000
Mar 04, 2012 2012-03-04 00:00:00.000
You can use the same calculation for a variable:
DECLARE
#y NVARCHAR(15) = N'18-Sept-2012',
#z DATETIME;
SELECT #z = CONVERT(DATETIME,z) FROM
(
SELECT SUBSTRING(y,s+1,3) + ' ' + LEFT(y,s-1) + ', ' + RIGHT(y,4) FROM
(
SELECT #y, CHARINDEX('-',#y)
) AS y(y,s)
) AS z(z);
SELECT #z;
-- UPDATE ...
(Now try with SET LANGUAGE FRENCH; and watch it all go to, well, somewhere.)
For this reason I highly recommend you stop storing / passing dates using the nvarchar type. We have strongly typed date/time types for a reason. When you need to pass a string literal, you should be using unambiguous, standard formats that aren't prone to differences in language, regional and dateformat settings. In this case the right format should be YYYYMMDD:
20120918
For more info, see:
Bad habits to kick : mis-handling date / range queries