title: Can a database attribute be primary and foreign key?
body: <p>I have 2 tables, <code>User</code> and <code>Employee</code>. Each user is given a <code>User_ID</code> and that is a primary key in the <code>User</code> table and a foreign key in the <code>Employee</code> table. Can that attribute in the <code>Employee</code> table also be a primary key?</p>