title: Finding percentages with this query
body: <p>The question is:
  Query 4. Write a query to list out the product names and the percentage of customers that have
  ordered the product. Format the percentage with the percentage symbol.</p>
  <p>What I have so far:</p>
  <pre><code>SELECT productName, CONCAT(ROUND(Products.productCode/(SELECT SUM(customerNumber) FROM Customers)*100, 2), '%') AS CustomerPercentage FROM Customers
  JOIN Orders ON Orders.customerNumber = Customers.customerNumber
  JOIN OrderDetails ON OrderDetails.orderNumber = Orders.orderNumber
  JOIN Products ON Products.productCode = OrderDetails.productCode
  GROUP BY Products.productCode;
  </code></pre>
  <p>When I do this I keep getting 0% for all values. What should I do to prevent this error from continuously occurring?</p>