Is it possible to set a unique constraint on a dataset column but still allow null values?

[Tim Frawley]

Is it possible to set a unique constraint on a dataset column but
still allow null values?

 

[Russell Jones]

Yes, although after applying the constraint you may have only one row with a
null value in that column.

 

[Tim Frawley]

Ok, that is completely understandable, thank you Russell.

What I really need is a way to make sure that entries are unique while
allowing multiple null values. It works through a grid so limiting the
rows in the grid is not an option.

The only way I can see to do it is to create a dataview and filter that
for the new entries prior to setting the value on the grid. I was
hoping for something in the dataset rather than a function that fires
each time a value is created.

 

[Jeffrey Tan[MSFT]]

Hi Tim,

If your columns has a unique constraint, that means it is a primary key
column. So all the items in the column must be unique. You can not have
multi-items in that column are null values.(This will violate the unique
constraint)

I think if you still want to apply multi-null values to your column, you
should remove the unique constraint from that column.

Best regards,
Jeffrey Tan
Microsoft Online Partner Support
Get Secure! - www.microsoft.com/security
This posting is provided "as is" with no warranties and confers no rights.

 

[Jeffrey Tan[MSFT]]

Hi Tim,

Does the community's reply make sense to you?

Please feel free to feedback. Thanks

Best regards,
Jeffrey Tan
Microsoft Online Partner Support
Get Secure! - www.microsoft.com/security
This posting is provided "as is" with no warranties and confers no rights.