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Editorial Team
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Asked: 2026-06-04T09:48:19+00:00

I have table that describes association of two other business models. Example: Construction Table

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I have table that describes association of two other business models.

Example:

Construction Table - available constructions |
Reader Table - available readers |
ReaderPlacement Table - reader assigned to specific construction for specific time.

According to my requirements ReaderPlacement table must contains ApiKey, for me best match is unique GUID used later on for WCF communication.

I am planning to write something like this:

ApiKey CHAR(36) NOT NULL DEFAULT NewSequentialId()

Is it the right solution? I read that NewSequentialId() is better than NewId() and should be unique.

Does db engine will protect my column to be unique when I use NewSequentialId() or I have to add any constraint and additional checks ?

It must be also valid with SQL Azure.

Cheers,
Daniel

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1 Answer

  1. Editorial Team

    Just by defining a default of newsequentialid(), there is no guarantee that you won’t have duplicates. Yes – the values generated by SQL Server will have an extremely high likelihood of being unique. But that default constraint doesn’t prevent you from inserting explicit values – and those could possibly collide with existing values.

    If your column ApiKey needs to be unique at all times, you must add a unique constraint

    ALTER TABLE dbo.ReaderPlacement
ADD CONSTRAINT UC_ReaderPlacement_ApiKey UNIQUE(ApiKey)

    With this unique constraint in place (which should definitely also work on SQL Azure), then SQL Server will prevent any duplicates from being inserted – any transaction attemting to do so will be terminated with an error message.

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