Question

I have the following table set up:

• Id int pk, unique not null
• Name varchar(50) not null
• Other columns not relevant to this issue

With an index set up on Name to be unique and non-clustered.

The setup does EXACTLY what I want – that is, only insert new rows whose Name doesn’t already exist in the table, and throw an error if the new row is a duplicate Name.

I might be nit-picky about it, but every attempt to add a duplicate will cause SQL Server to skip the next Id that would have been assigned, had the new row been a non-duplicate Name.

Is there a way to prevent this with some setting, without the need to query for existence first before deciding to insert or deny?

Answer 1

No, there is no setting to prevent the identity value from incrementing on a failed insert.

Like you suggest, you can mitigate this by checking for a duplicate before performing the insert – I would do this not just to keep the identity from incrementing, but also to keep your Sql Server from raising errors as a standard procedure.

However, there may be other exceptional circumstances that would cause an insert to fail… so if gaps in the Ids pose more than an aesthetic problem, an identity column might not be the best solution for what you’re trying to solve.