converting varchar to date format in sql server - sql

Question

I have a table with two date column. However the columns are in varchar. I need to covert them as date format.
The sample data is like this:
Account Number | Registration Date | System Status Change Date
01740567715 | 10-JUL-13 | 30-JUL-13 12.53.32.000000000 PM
I want both of these columns like this: 10-Jul-2013.
For Registration Date, I am using this code:
Update [dbo].[SysDataV2]
Set ["REGISTRATION_DATE"]= convert(datetime, (["REGISTRATION_DATE"]), 106)
But it is shwoing the result as varchar and also showing erroneous format.
For System Status Change Date I am using following code:
update [dbo].[SysData]
Set ["KYC_STATUS_CHANGED_DATE"]= REPLACE(CONVERT(datetime,convert(datetime,left(["KYC_STATUS_CHANGED_DATE"],9),103),106),' ' ,'-')
Both are changing to date format of some type (not my expected format) but in table structure they are still shown as varchar.
What am I doing wrong here?

Answer 1

The table's data type is still varchar. An update merely changes the string, it doesn't change the data type. What you should do is (assuming all of the dates are valid and this format is 100% consistent):
UPDATE dbo.SysData SET REGISTRATION_DATE =
CONVERT(CHAR(10), CONVERT(DATE, REGISTRATION_DATE, 106), 120);
UPDATE dbo.SysData SET KYC_STATUS_CHANGED_DATE =
CONVERT(CHAR(10), CONVERT(DATETIME, LEFT(KYC_STATUS_CHANGED_DATE, 9), 106), 120)
+ REPLACE(SUBSTRING(KYC_STATUS_CHANGED_DATE, 10, 9), '.',':')
+ RIGHT(KYC_STATUS_CHANGED_DATE, 2);
ALTER TABLE dbo.SysData ALTER COLUMN REGISTRATION_DATE DATE;
ALTER TABLE dbo.SysData ALTER COLUMN KYC_STATUS_CHANGED_DATE DATETIME;
And then stop inserting regional and potentially problematic strings. String literals representing dates / datetimes should be:
-- date only
YYYYMMDD
-- with time:
YYYY-MM-DDThh:mm:ss.nnn
But best is to simply make sure they are date or datetime values before you ever hand them off to SQL Server. Your application should be able to do this without ever converting to some arbitrary string format. Never, ever, ever store date or datetime values as strings in SQL Server. You gain nothing and you lose quite a lot.

Answer 2

You need to change the data type of the column from a varchar to store it as a Date. Then when you select it you can format it any way that you like. One way to do this would be to create a new column of the correct datatype and convert the data, then remove the old column. Make sure the the old column doesn't have and foreign key relationships or you will also need to transfer those over as well.
ALTER TABLE [dbo].[SysData] ADD ConvertedDate DateTime
UPDATE [dbo].[SysData] SET ConvertedDate = CAST(VarCharDate as DateTime)
ALTER TABLE [dbo].[SysData] DROP COLUMN VarCharDate