title: Dot Notation in SQL FROM clause
body: <p>I'm trying to understand some example SQL code (without extra context, apart from the fact that it's Postgres).  I can't for the life of me work out what the dot notation in the following line means:</p>
  
  <pre><code>SELECT user_id INTO id FROM customer.user WHERE user_id=1;
  </code></pre>
  
  <p>What could 'customer.user' refer to exactly? What does this dot notation mean?</p>