title: SQL make a list of not existing objects
body: <p>I have following problem. 
  Two tables. Product Table and Inventory Table. </p>
  
  <p>In Product table are a list of all possible products and in Inventory the current stock of each store</p>
  
  <p>e.g. 
  Inventory Table</p>
  
  <pre><code>ProductID     Stock     StoreID
  1             10        1
  2             10        1
  3             10        1
  1             10        2
  </code></pre>
  
  <p>Product Table</p>
  
  <pre><code>ProductID     Product     
  1             Bananas        
  2             Apples 
  3             Oranges
  4             Kiwi
  </code></pre>
  
  <p>What I want is a list of products that are not in stock for the stores.
  Following the example the desired result would be</p>
  
  <pre><code>Store ProductID  Product
  1     4          Kiwi 
  2     2          Apples
  2     3          Oranges 
  2     4          Kiwi
  </code></pre>
  
  <p>Now I tried several approaches from left joins, not in and not exist but haven't found a solution. 
  E.g.</p>
  
  <pre><code>SELECT * 
  FROM Inventory t1 
  left join Product t2 ON t2.ProductID = t1.ProductID 
  WHERE t2.ProductID IS NULL 
  </code></pre>
  
  <p>But this returns nothing</p>
  
  <p>Any help please. </p>
  
  <p>Thank you</p>