title: What's the difference between "INNER JOIN" and "Conjunctive Query"?
body: <p>Assuming I have two tables : <code>users</code> and <code>products</code>. </p>
  
  <p>users</p>
  
  <pre><code>uid | name
  -------------
  1   | Peter
  2   | Mary
  3   | Ben
  </code></pre>
  
  <p>products</p>
  
  <pre><code>pid | product | uid
  -------------------------
  1   | apple   | 2
  2   | lemon   | 2
  3   | banana  | 2
  4   | orange  | 3
  </code></pre>
  
  <p>What is the difference between:</p>
  
  <pre><code>SELECT p.*, u.name FROM products p INNER JOIN users u ON p.uid = u.uid
  </code></pre>
  
  <p>and</p>
  
  <pre><code>SELECT p.*, u.name FROM products p, users u WHERE p.uid = u.uid 
  </code></pre>
  
  <p>Are they "logically" the same? (which both gives the intersection of the two tables)</p>
  
  <p>Also, is there any performance difference between them?</p>