title: combine two columns en sort asc
body: <p>I've a question about the order by function of MySQL. </p>
  
  <p>In the DB a have rows with two prices. price_min and price_max. For example: </p>
  
  <pre><code>ID | NAME   | PRICE_MIN | PRICE_MAX
  1  | NAME A | 100       | 350
  2  | NAME B | 0         | 250
  3  | NAME C | 0         | 90
  4  | NAME D | 125       | 500
  5  | NAME E | 50        | 0
  6  | NAME F | 25        | 0
  </code></pre>
  
  <p>I want to have a query that both columns is sorting from low to high. And if possible showing the rows where the price is MIN and Max double. So in this example i will get 8 results like: </p>
  
  <p>ID: 6, 5, 3, 1, 4, 2, 1, 4. </p>
  
  <p>Is this possible and how will I do that? </p>