title: SQL query to find missing values in tables
body: <p>Table 1</p>
  
  <pre><code>Product    product Description
  ABC        Hardware
  CBD        Software
  BCQ        Component
  DEF        License
  </code></pre>
  
  <p>Table 2</p>
  
  <pre><code>Product  Product Description Order ID
  ABC      Hardware            1234
  ABC      Hardware            2345
  ABC      Hardware            5678
  BCQ      Component           7896
  BCQ      Component           9681
  </code></pre>
  
  <p>Here is the background
  table 1 has the product data, table 2 has the product data with order ids
  I want to know how many products are not ordered (in this scenario "CBD     Software" and "DEF     License" has not orders placed hence is missing in table 2).
  now i want to know how many products were never placed on an order.</p>