title: creating a table with reference to a non primary key column
body: <p>I have two tables Users &amp; Stores</p>
  
  <p>Users table primary key is combination of address &amp; phone number (users enroll through a web page and I don't want the same user to enroll twice), the userId column is serial but not a primary key</p>
  
  <p>In Stores table the column of ownerID is it's userID from the users table - but since it's not primary key the reference can not be set (although it's serial)</p>
  
  <p>how can I achieve this result?</p>