title: How to retrieve the name of every customer and how many pizzas they have ordered?
body: <p>I have to retrieve the name of every customer and how many pizzas they have ordered. NULL if no pizzas ordered.</p>
  
  <pre><code>SELECT blank 1
  FROM blank 2(
  SELECT blank 3 AS quantity
       FROM ORDERS NATURAL JOIN ORDERCONTENTS
       GROUP BY blank 4) as quantity
  ON customers.customerID=quantity.customerID
  ORDER BY name;
  </code></pre>
  
  <p>The database contains 5 tables in this layout:</p>
  
  <pre><code>Customers
      columns
         customerID,
         name,
         address,
         phoneNumber,
         email
  
  Ordercontents
      columns
          orderID,
          name,
          quantity
  orders
      columns
         orderID,
         customerID,
         postcode,
         Date
  
  products
      columns
         name,
         price
  
  stores 
      columns
         postcode,
         address,
         phoneNumber
  </code></pre>
  
  <p>The numbered blanks have to be replaced to produce the outcome.</p>