title: Will the "Sub" claim in an Auth0 JWT always be unique?
body: <p>I just have a quick Auth0 question. I've looked all over, but the more I look the more confused I get. </p>
  
  <p>In the payload of the JWT that Auth0 gives me when I log in there is a Sub claim that look like this "sub": "facebook|123456789".</p>
  
  <p>I'm just curious if sub will always be unique and if I can use it as a sort of foreign key in my database to link users to different tables. </p>