Question

I have the following structure:

-- Table Users ---
-  User1
-  User2
-  User3

-- Table Roles ---
-  Role1
-  Role2
-  Role3
-  Role4

Every user has to have one row, not more or less. Should i create a new table, eg. `user_roles” and store the users role in there, like:

-- Table user_roles --
-  user_id = User1     role_id = Role2
-  user_id = User2     role_id = Role1
-  user_id = User3     role_id = Role4

Or, should I store the users role in the Users table? Since there will always only be one role for each user, I see no reason why not to keep it in the Users table. Am I thinking correctly or should it be in a separate table? Very simple question, but I’ve wondered for long. In the past I have kept the “key” in the Users table.

Answer 1

To enforce that every use has to have exactly one role, you should add a role_id to the users table, make it not null and reference the roles table

create table roles 
(
  id integer primary key,
  role_name varchar(50) not null
);

create table users
(
   id integer not null primary key,
   username varchar(50) not null,
   role_id integer not null,
   ... other columns ...
);
alter table users 
   add constraint fk_users_rol 
   foreign key (role_id) references roles(id);