title: select all products and their category names
body: <p>I have 2 tables like this :  </p>
  
  <p><code>product(id_product,reference,category_id)</code>  </p>
  
  <p>and</p>
  
  <p><code>category(category_id,category)</code></p>
  
  <p>How can I output every product plus his category name?</p>