title: Error 1064 - In statement
body: <p>I am trying to show the average price of products bought by customers from ‘Tucson’, however this query returns <code>null</code> even though there are two customers that have placed orders from Tuscon.</p>
  
  <pre><code>select AVG(product_price) from product where product_id in
  (select product_id from orderline where order_id in
  (select order_id from ordertable where cust_id in
  (Select cust_id from customer where city = 'Tuscon')))
  </code></pre>