title: Mysql - Get id from string array column and order
body: <p>this is a bit tricky.
  I have a mysql table representing users, each user has a categories column that is delimited with &lt;..> - </p>
  
  <pre><code>id       Categories
  1        &lt;1&gt;&lt;5&gt;&lt;7&gt;
  2        &lt;2&gt;&lt;5&gt;&lt;6&gt;
  3        &lt;2&gt;&lt;4&gt;&lt;5&gt;&lt;6&gt;
  4        &lt;2&gt;&lt;5&gt;&lt;7&gt;&lt;9&gt;
  5        &lt;3&gt;&lt;2&gt;&lt;8&gt;
  ...
  </code></pre>
  
  <p>Now, I receive an array with a list of categories (i.e - 1, 3, 6), and I need to fetch the rows that contain those categories, and also ORDERED according to their place in the array - 1 is most important, after that 3 and last is 6.
  In this example I should receive rows 1, 5, 2, 3.
  Any suggestion for a clean and fast query?
  Thanks!</p>