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Easiest way to make a column unique
Message
Information générale
Forum:
Microsoft SQL Server
Catégorie:
Conception bases de données
Divers
Thread ID:
00620370
Message ID:
00621291
Vues:
11
>What is the easiest way to make column unique?
>
>I created a unique index on the field but I really dont need the index, so the overhead of the managing the index seems excessive. Is there any other way to make a column unique? Im thinking some sort of check constraint that does a select but I get an error every time I use a query in a check constraint.
>
>Any ideas?
>
>Eric

From the BOL:

"SQL Server automatically creates a UNIQUE index to enforce the uniqueness requirement of the UNIQUE constraint. Therefore, if an attempt to insert a duplicate row is made, SQL Server returns an error message that says the UNIQUE constraint has been violated and does not add the row to the table. Unless a clustered index is explicitly specified, a unique, nonclustered index is created by default to enforce the UNIQUE constraint."

You complain about overhead... but, whould you rather have SQL Scan the whole table each time you add/update a record to make sure the value is unique?
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