title: Delete selected rows in mysql
body: <p>I would like to delete set of rows, which have same property like this SQL select.</p>
  
  <pre><code>SELECT item_id, count(*) as item_in_order
  FROM items
  GROUP BY order_id
  HAVING item_in_order = 1
  </code></pre>
  
  <p>In words it means, that I have items of orders and I would like to delete rows, which are from orders with only one Item.</p>
  
  <p>For example:</p>
  
  <pre><code>item_id    order_id
  1          1
  2          2
  3          2
  4          3
  5          3
  6          4
  </code></pre>
  
  <p>So I would like to delete rows with item_id 1 and 6.</p>