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Editorial Team
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Asked: 2026-06-10T02:21:55+00:00

I’m trying to use migrations to add a parent table to an existing child

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I’m trying to use migrations to add a parent table to an existing child table. For eg. I currently have User table, now I want to add a Department table that has a 1 to many relationship: Department has many User.

My questions, in automatic update, can I somehow seed the parent table before adding the FK so I can update all the children to this default seeded Department? If automatic update cannot do this, how do I accomplish this in code?

What I currently did: Made the FK nullable, created the Parent and seeded it, then update all child User FK to the parent. But now I cant change the FK not nullable because throws this error: Automatic migration was not applied because it would result in data loss.

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  1. Editorial Team

    Switching from nullable to non-nullable is considered data loss because after the migration, there is no way to tell which rows (if any) were null. If you are ok with this, you can call Update-Database with the -Force flag.

    Another option would be to add a code-based migration that would:

    1. Add the Departments table
    2. Insert a default department
    3. Add the required FK column to User with a default value of the inserted department
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