title: mysql query to include null values in where clause
body: <p>I have a table member1 which looks like this. I am editing my table why I want to return all values from pst.</p>
  
  <pre><code>id  club_id mobile      pst
  1     1     9437054788  6
  2     1     9437345602  NULL
  3     2     9437056738  35
  4     2     9437064876  39
  5     1     9437059927  NULL
  6     2     9437965276  40
  7     1     9437121455  NULL
  </code></pre>
  
  <p>I have a drop-down fields one for club_id and another check-box field for pst with a value of 'select All' on both fields. 'select All' equals '%'.</p>
  
  <p>The solution provided by @TheConstructor works well in this query</p>
  
  <pre><code>SELECT group_concat(mobile) FROM `member1` WHERE COALESCE(pst, '') 
  LIKE '%' and club_id=1
  </code></pre>
  
  <p>or </p>
  
  <pre><code>SELECT group_concat(mobile) FROM `member1` WHERE COALESCE(pst, '') 
  LIKE '6' and club_id=1
  </code></pre>
  
  <p>Now I want to have multiple values in the query in place of '6' for example</p>
  
  <pre><code>SELECT group_concat(mobile) FROM `member1` WHERE COALESCE(pst, '') 
  in (6,35,39,40) or in ('%') and club_id=1
  </code></pre>
  
  <p>How I can achieve that, as at the moment I can return the result with just one value i.e. 6 or 35 or 39 or 40</p>