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Asked: 2026-05-28T13:49:08+00:00

I’d like to setup a foreign key to a default membership table but I’m

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I’d like to setup a foreign key to a default membership table but I’m getting an error when trying to define it. I’m using the default aspnet_Users table and also my own Posts table. I’m trying to setup the tables as follows:

aspnet_Users

  • UserId (PK) uniqueidentifier
  • UserName nvarchar(256)

Posts

  • PostID (PK) int
  • UserName (FK -> aspnet_Users.UserName) nvarchar(256)

However, when I try to set this up using the VS 2010 designer, it gives me the following error:

The columns in table 'aspnet_Users' do not match an existing primary key
or unique constraint.

Is this not working because aspnet_Users.UserName isn’t a part of the PK for aspnet_Users? I’ve tried to change the table to include that as part of the PK (I think that makes it a composite key?) but it’s telling me to delete the relationships first before I can do it. Being as I don’t know what relationships the default membership tables define, I’d rather find out more before going that route.

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1 Answer

  1. Editorial Team

    The error message is fully describing the situation – you’re trying to use a non-key field inside a foreign key constraint. You suggest trying to create a composite key to get around this issue, which would work, but why wouldn’t you simply use the existing primary key?

    The UserID field is a uniqueidentifier PK, so it is already configured for use in a FK. And, you’d be utilizing normalization, so that rather than storing (up to) 256 bytes per Username on each row, you’d only be storing the uniqueidentifier (16 bytes).

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