title: How to query SQL rows HAVING NOT (array values) in a field with comma separated values?
body: <p>I have a SQL table, which looks like this:</p>
  
  <p><strong>id_question (int)</strong> | <strong>tags (varchar)</strong><br>
  where "tags" field is<br>
  - either empty : NULL<br>
  - or is filled with one value (Ex: 1) (not numeric)<br>
  - or is filled with several comma separated values (ex: 273,2308,24) (not numeric)</p>
  
  <p><strong>id_question (int)</strong> | <strong>tags (varchar)</strong><br>
  1 | 1,373<br>
  2 | 283,4555,308,12<br>
  3 | 283,25,3  </p>
  
  <p>ANd i have a blacklisted_tags array.
  I would like to retrieve id_questions of all questions whose tags field do not have a blacklisted  $tags_blacklist value.</p>
  
  <p><strong>For example:</strong><br>
  $tags_blacklist = array (1,3)<br>
  => I should get 2<br>
  and not 1 because it has 1 in its tags field<br>
  and not 3 because it has 3 in its tags field.</p>
  
  <p>What should my SQL query look like?</p>