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SQL Server table date field to delete a date and accept a null or blank

Posted on 2011-02-14
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Last Modified: 2012-06-27
I have a VB.Net edit form with a date field that is optional.  Somtimes a date will be added and at other times the user will delete the date and leave it blank.  The sql field is set to accept nulls and is fine if it is left blank.  When I add a date and then delete a date, I get a sql error that the date format is not correct.  how do I get the table to accept the blank as a null again?
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Question by:rtay
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Expert Comment

by:Sharath
ID: 34892234
What is your error? You can add blank value to the date field.
declare @table table(col datetime)
insert @table values (null),(GETDATE()),('')
select * from @table
/*
col
NULL
2011-02-14 14:04:47.063
1900-01-01 00:00:00.000
*/

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Expert Comment

by:lundnak
ID: 34892236
You needs to pass a null value to the date field.  Make sure it isn't an empty set value.
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Expert Comment

by:Olaf Doschke
ID: 34892309
SQL Server does implicit data type conversions of strings to dates/datetimes, but does not convert empty strings to NULL.

Check out DBNull.Value. Eg you set Object.Datetimefield = DBNull.Value in VB.NET before saving.

Bye, Olaf.
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Accepted Solution

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CodeCruiser earned 2000 total points
ID: 34895594
I think the problem is not with the SQL Server but with the control being used. The DateTimePicker does not support Null as its date value.

Try one of these nullable datetimepickers

http://www.codeproject.com/KB/selection/Nullable_DateTimePicker.aspx

http://www.codeproject.com/KB/selection/NullableDateTimePicker.aspx

http://www.codeproject.com/KB/selection/NDTP_VS2008.aspx
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