title: Select with priority order
body: <p>It's my table, <code>CAR</code> :</p>
  
  <pre><code>+------+--------+---------+
  | id   | model  | color   |
  +------+--------+---------+
  | 1    | bmw    | blue    |
  | 2    | bmw    | red     |
  | 3    | bmw    | null    |
  | 4    | porsche| null    |
  | 5    | porsche| red     |
  | 6    | vw     | orange  |
  | 7    | car    | null    |
  +------+-------+----------+
  </code></pre>
  
  <p>How to select all distincts models with this priority of color :</p>
  
  <ol>
  <li><code>blue</code> </li>
  <li><code>red</code></li>
  <li><code>null</code> or other colors...</li>
  </ol>
  
  <p>?</p>
  
  <p>The result of the query would be something like that :</p>
  
  <pre><code>+------+--------+
  | id   | model  |
  +------+--------+
  | 1    | bmw    |
  | 5    | porsche|
  | 6    | vw     |
  | 7    | car    |
  +------+--------+
  </code></pre>