Question

I am thinking about a schema design that involves having users and user roles, but I am not sure what would be the better route.

Option 1

Create three tables, one with the user information, one with the role information, and one with th user role relation.

users {
    u_id,
    etc
}

roles {
   r_id,
   r_name,
   etc
}

user_roles {
   u_idm
   r_id
}

Option 2

Create two tables, one with the user information, and the other with role, role info,and relation info.

users {
    u_id,
    etc
}

roles {
   r_id,
   u_id,
   r_name,
   etc
}

Option 1 is more robust but requires an extra join. Option 2 will require an extra primary key but will only be one join. If I ever change the role name, it would take longer to update with option, but I don’t forsee updates being frequent.

For a scalable solution, which would be better? What other insights in my missing? This is for a mysql and postgresql solution.

Answer 1

Option 1.
What good is a role if only one user can have each role?
If you have 100 registered users there would be 100 duplicate definitions for “registered user”.

The more “etc” there is the bigger your db will get.

Having that many duplicates will slow down your database and in the end things will be a lot slower even if you have one join less.

If you run lots of role based querys and relly eel like you need a database like the one from option two you can still create a view and have the database cache it, but I doubt that this will do you any good.