Question

This is my table, GameAdmin:

game_id   company_id    user_id
1         5             NULL
1         5             NULL
1         NULL          2
1         NULL          3
1         NULL          3

It links games to entities that can edit them (either a company or a user).

I have a UNIQUE index on all columns, but as you can see it’s not working as expected.

What is wrong? Is it because of the NULLs?

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I know I could make it work by changing the structure to:

game_id   admin_type    admin_id
1         company       5
1         company       5
1         user          2
1         user          3
1         user          3

But that’s not compatible with my JPA/Hibernate setup, or at least very inconvenient, because it doesn’t allow me to set the relations like this:

@ManyToOne(optional=true)
private User user;

@ManyToOne(optional=true)
private Company company;

Answer 1

Oh, the solution is so simple. I split the constraint up, so there’s one for game_id and company_id, and for game_id and user_id.