Converting NVARCHAR to SMALLDATETIME on SQL SERVER 2008 - sql

Question

I'm currently working on updating company database in which on one of the tables the CreateDt is in the nvarchar(20) type and stores dates in the following ways:
12 May 12
29/03/2011
9/24/2012
29/01/2001 08:51:56
There are 17,000 rows.
So I'm currently working on code in which I will be able to convert these dates all into the one format such as DD-MM-YYYY.
However I'm struggling to find anything suitable.
So far I have tried:
WITH CreateDt1
AS
(
SELECT '14 DECEMBER 12' AS CreateDt1
UNION ALL
SELECT '13/10/2005'
UNION ALL
SELECT '12/14/2012'
UNION ALL
SELECT '24/05/2002 09:28:58'
UNION ALL
SELECT '28/02/2011'
)
SELECT
CreateDt1,
CASE WHEN ISDATE(CreateDt1) = 1
THEN CAST(CreateDt1 AS datetime)
ELSE
CASE WHEN SUBSTRING(CreateDt1, 3, 1) = '/'
THEN
CASE WHEN ISDATE(SUBSTRING(CreateDt1, 4, 2) + '/' + LEFT(CreateDt1, 2) + '/' + RIGHT (CreateDt1, 4)) = 1
THEN CAST(SUBSTRING(CreateDt1, 4, 2) + '/' + LEFT(CreateDt1 , 2) + '/' + RIGHT (CreateDt1, 4) AS datetime)
END
END
END AS NewDate
FROM fct_Project;
However this returns null values for dates such as 29/01/2001 08:51:56.

Answer 1

Try add LEFT function in RIGHT to your query in case clause like:
CASE WHEN ISDATE(CreateDt1) = 1
THEN CAST(CreateDt1 AS datetime)
ELSE
CASE WHEN SUBSTRING(CreateDt1, 3, 1) = '/'
THEN
CASE WHEN ISDATE(SUBSTRING(CreateDt1, 4, 2) + '/' + LEFT(CreateDt1, 2) + '/' + RIGHT (LEFT(CreateDt1,10), 4)) = 1
THEN CAST(SUBSTRING(CreateDt1, 4, 2) + '/' + LEFT(CreateDt1 , 2) + '/' + RIGHT (LEFT(CreateDt1,10), 4) AS datetime)
END
END
END AS NewDate

Answer 2

I've just edited your code by adding a few lines, hope it will help.
Keep in mind, that it does not solve problem of 10/11 and 11/10 cases.
WITH CreateDt1
AS
(
SELECT '14 DECEMBER 12' AS CreateDt1
UNION ALL
SELECT '13/10/2005'
UNION ALL
SELECT '12/14/2012'
UNION ALL
SELECT '24/05/2002 09:28:58'
UNION ALL
SELECT '28/02/2011'
)
SELECT
CASE WHEN ISDATE(CreateDt1) = 1
THEN CAST(CreateDt1 AS datetime)
ELSE
CASE WHEN SUBSTRING(CreateDt1, 3, 1) = '/'
THEN
CASE WHEN ISDATE(SUBSTRING(CreateDt1, 4, 2) + '/' + LEFT(CreateDt1, 2) + '/' + RIGHT (CreateDt1, 4)) = 1
THEN CAST(SUBSTRING(CreateDt1, 4, 2) + '/' + LEFT(CreateDt1 , 2) + '/' + RIGHT (CreateDt1, 4) AS datetime)
WHEN ISDATE(SUBSTRING(CreateDt1, 4, 2) + '/' + LEFT(CreateDt1, 2) + '/' + LEFT((RIGHT (CreateDt1, 13)),4) ) = 1
THEN CAST ( (SUBSTRING(CreateDt1, 4, 2) + '/' + LEFT(CreateDt1, 2) + '/' + LEFT((RIGHT (CreateDt1, 13)),4) ) AS DATETIME)
END
END
END AS NewDate
FROM CreateDt1;