I mean at the database level. Your relationships are foreign keys and they're 1:N. Yes, you can try and artificially limit them to 1:1 using constraints but it

I mean at the database level. Your relationships are foreign keys and they're 1:N. Yes, you can try and artificially limit them to 1:1 using constraints but it's a hack. The correct way to represent a 1:1 relationship in a database is with one table.