[Webinar] Streamline your web hosting managementRegister Today

x
  • Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 107
  • Last Modified:

SQL syntax to delelte data is not a date format

I am importing data from a third party software
One of the fields they have is an nvarchar(200) but holds dates in format :  mm/dd/yyyy

Most of the entries in that field are in fact dates, but some aren't. I need to delete any entries in that field which are NOT a 'date' or in date format 'mm/dd/yyyy'

The table name is:  Dependents
The field name is:  DepLastUSEntry

Also some dates are in :  07/27/03

Can they be converted to :  07/27/2003  ?
And also:  8/25/2003  into 08/25/2003  
Maybe:  8/13.2002  into 08/13/2002

Anything different that cannot be converted into a mm/dd/yyyy should be deleted, and if the conversions above cannot be done then remove any date that is not mm/dd/yyyy




Thanks!
0
Aleks
Asked:
Aleks
  • 3
  • 3
1 Solution
 
Olaf DoschkeSoftware DeveloperCommented:
Which SQL Server version are you using (SELECT @@Version)?

Starting wioth 2012 you may use:

SET LANGUAGE ENGLISH -- importatnt to process dates in format mm/dd/yyyy, might be optional if your server setting is in english/british/us format anyway.
DELETE FROM yourtable WHERE TRY_CONVERT(date, DepLastUSEntry) IS NULL

Open in new window


Just try some dates (especially with day>12) on try_convert to see whether it results in a date for correct nvarchar strings, so you don't delete everything.

Bye, Olaf.
0
 
Jim HornMicrosoft SQL Server Developer, Architect, and AuthorCommented:
>I need to delete any entries in that field which are NOT a 'date' or in date format 'mm/dd/yyyy'
DELETE means remove the entire row from the table.
UPDATE means change values in the row, say changing this column to an empty string or NULL '', and keep the row.

Tell us which you wish to do here.
0
 
AleksAuthor Commented:
Sorry. I meant update and make it null
0
Never miss a deadline with monday.com

The revolutionary project management tool is here!   Plan visually with a single glance and make sure your projects get done.

 
Olaf DoschkeSoftware DeveloperCommented:
Well, then you would UPDATE instead of delete, but you can't update an nvarchar column with a date, you can only set those NULL, which aren't a date in string form.

SET LANGUAGE ENGLISH -- important to process dates in format mm/dd/yyyy, might be optional if your server setting is in english/british/us format anyway.
UPDATE yourtable SET DepLastUSEntry = NULL 
WHERE TRY_CONVERT(date, DepLastUSEntry) IS NULL

Open in new window


Again, test before you do, with the wrong settings (eg TRY_CONVERT converting dd/mm/yyyy instead of mm/dd/yyyy, international formats differ a lot also in regard of the dash separator) you may lose part of the dates you rather wanted to keep.

If your overall goal is to alter the table to have a date or datetime column:

Set Language English;
Create Table #Test (DepLastUSEntry nvarchar(200));
Insert Into #Test Values (N'12/31/2010'), (N'31/12/2015');
Select * From #Test;

Update #Test set DepLastUSEntry = NULL WHERE TRY_CONVERT(date,DepLastUSEntry) IS NULL;

Alter Table #Test Alter Column DepLastUSEntry Date NULL;
Select * From #Test;
Drop Table #Test;

Open in new window


You would execute lines 1, 6, and 8 only, obviously.

Bye, Olaf.
0
 
AleksAuthor Commented:
I tried this, but I am using SQL 2008R2

SET LANGUAGE ENGLISH -- important to process dates in format mm/dd/yyyy, might be optional if your server setting is in english/british/us format anyway.
UPDATE yourtable SET DepLastUSEntry = NULL 
WHERE TRY_CONVERT(date, DepLastUSEntry) IS NULL

Open in new window


Error

Msg 195, Level 15, State 10, Line 5
'TRY_CONVERT' is not a recognized built-in function name.

Open in new window

0
 
Olaf DoschkeSoftware DeveloperCommented:
That's why I asked for the version. Then try it with ISDATE():

First see, if these dates are correct:
SELECT DepLastUSEntry FROM yourtable WHERE ISDATE(DepLastUSEntry)=1

Open in new window


If so, this update will change all other invalid ones to NULL:
UPDATE yourtable SET DepLastUSEntry = NULL 
WHERE ISDATE(DepLastUSEntry)=0

Open in new window

Bye, Olaf.
0
 
AleksAuthor Commented:
This worked!
0

Featured Post

Upgrade your Question Security!

Your question, your audience. Choose who sees your identity—and your question—with question security.

  • 3
  • 3
Tackle projects and never again get stuck behind a technical roadblock.
Join Now