Do not allow duplicates

[dbaldwin117]

I need to use a key field that is not indexed, but will not allow duplicates. How can this be done?

 

[MarkK]

I believe the index is the mechanism used to identity duplicates, so I doubt you can have it both ways.
You could write your own duplicate finder, but on a non-indexed field it would be slow.
Generally I think an index is a small price to pay to allow you to disallow duplicates.

 

[Galaxiom]

Lagbolt is correct about the indexes. I can't imagine why anyone would have this requirement.

Maybe there is a terminology issue and the OP actually wants a Key field that is not Autonumbered. If so, set the field's datatype to Number.