title: Return distinct and null records from a mysql join query
body: <p>Is there any way to return distinct values with blank/null data from a table join. Best to explain with my example below.</p>
  
  <p>Table "orders"</p>
  
  <pre><code>order_id | order_total
  1        | 10
  2        | 20
  3        | 50
  </code></pre>
  
  <p>Table "order_items"</p>
  
  <pre><code>item_id | order_id | name     | qty_ordered | base_price | row_total
  1       | 1        | Product  | 1           | 10         | 10
  2       | 2        | Product  | 1           | 10         | 10
  3       | 2        | Product2 | 1           | 10         | 10
  4       | 3        | Product  | 2           | 10         | 20
  5       | 3        | Product2 | 3           | 10         | 30
  </code></pre>
  
  <p>I'm trying to produce a result set that looks like this.</p>
  
  <pre><code>order_id | item_id | name     | qty_ordered | base_price | row_total | order_total
  1        | 1       | Product  | 1           | 10         | 10        | 10
  2        | 2       | Product  | 1           | 10         | 10        | 20
  null     | 3       | Product2 | 1           | 10         | 10        | null
  3        | 4       | Product  | 2           | 10         | 20        | 50
  null     | 5       | Product2 | 3           | 10         | 30        | null
  </code></pre>
  
  <p>I only want the order_id and order_total once per order. I figure this is possible with some sort of join/distinct/sub query but alas nothing I've tried has worked so far.</p>