title: Should every table have a primary key?
body: <p>I read somewhere saying that every table should have a primary key to fulfill 1NF.</p>
  
  <p>I have a tbl_friendship table.</p>
  
  <p>There are 2 fields in the table : Owner and Friend.</p>
  
  <p>Fields of Owner and Friends are foreign keys of auto increment id field in tbl_user.</p>
  
  <p>Should this tbl_friendship has a primary key?
  Should I create an auto increment id field in tbl_friendship and make it as primary key? </p>