title: Use of an ID in databases
body: <p>When creating a new table in a database, what is the importance of using id.  For our purposes, we are using unique username and email in each field to match the info with that unique username or email.  So what is the use of id?</p>
  
  <p>Also, what is the length/value field for? New to this.</p>
  
  <p>thanks a bunch!</p>