title: Group_Concat in Concat not working with NULL values
body: <p>I have a table</p>
  
  <pre><code>CREATE TABLE IF NOT EXISTS `dept` (
    `did` int(11) NOT NULL,
    `dname` varchar(50) DEFAULT NULL
  ) ENGINE=InnoDB DEFAULT CHARSET=latin1;
  
  INSERT INTO `dept` (`did`, `dname`) VALUES
  (1, 'Hi'),
  (2, NULL),
  (3, 'Hello');
  </code></pre>
  
  <p>Then I have a query</p>
  
  <pre><code>select group_concat(concat(did,"','",dname) separator '),(') as Result from dept
  </code></pre>
  
  <p>It is producing result as <code>1','Hi'),('3','Hello</code></p>
  
  <p><strong>Question:</strong> How can I get result from above query as <code>1','Hi'),('2','NULL'),('3','Hello</code></p>
  
  <p>It is missing the rows which have NULL values but I need to fetch all</p>
  
  <p><a href="http://sqlfiddle.com/#!2/158d5/1" rel="nofollow"><strong>Link for SQL Fiddle Demo of question</strong></a></p>
  
  <p><strong>UPDATE:</strong> If I have more than one or all columns allowing NULL, Is there some way to apply COALESCE once for all or have to apply individually at each Column? </p>