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Asked: 2026-05-10T19:45:11+00:00

We use GUIDs for primary key, which you know is clustered by default. When

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We use GUIDs for primary key, which you know is clustered by default.

When inserting a new row into a table it is inserted at a random page in the table (because GUIDs are random). This has a measurable performance impact because the DB will split data pages all the time (fragmentation). But the main reason I what a sequential GUID is because I want new rows to be inserted as the last row in the table… which will help when debugging.

I could make a clustered index on CreateDate, but our DB is auto-generated and in development, we need to do something extra to facilitate this. Also, CreateDate is not a good candidate for a clustered index.

Back in the day, I used Jimmy Nielsons COMB’s, but I was wondering if there is something in the .NET framework for this. In SQL 2005 Microsoft introduced newsequentialid() as an alternative to newid(), so I was hoping that they made a .NET equivalent because we generate the ID in the code.

PS: Please don’t start discussing if this is right or wrong, because GUIDs should be unique etc.

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  1. It should be possible to create a sequential GUID in c# or vb.net using an API call to UuidCreateSequential. The API declaration (C#) below has been taken from Pinvoke.net where you can also find a full example of how to call the function. 

    [DllImport('rpcrt4.dll', SetLastError=true)] static extern int UuidCreateSequential(out Guid guid);

    The MSDN article related to the UuidCreateSequential function can be found here which includes the prerequisites for use.

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