title: MySQL GROUP_CONCAT escaping
body: <p>(NOTE: This question is not about escaping queries, it's about escaping results)</p>
  
  <p>I'm using <a href="http://dev.mysql.com/doc/refman/5.0/en/group-by-functions.html#function_group-concat" rel="noreferrer">GROUP_CONCAT</a> to combine multiple rows into a comma delimited list. For example, assume I have the two (example) tables:</p>
  
  <pre><code>CREATE TABLE IF NOT EXISTS `Comment` (
  `id` int(11) unsigned NOT NULL auto_increment,
  `post_id` int(11) unsigned NOT NULL,
  `name` varchar(255) collate utf8_unicode_ci NOT NULL,
  `comment` varchar(255) collate utf8_unicode_ci NOT NULL,
  PRIMARY KEY  (`id`),
  KEY `post_id` (`post_id`)
  ) ENGINE=MyISAM  DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=6 ;
  
  INSERT INTO `Comment` (`id`, `post_id`, `name`, `comment`) VALUES
  (1, 1, 'bill', 'some comment'),
  (2, 1, 'john', 'another comment'),
  (3, 2, 'bill', 'blah'),
  (4, 3, 'john', 'asdf'),
  (5, 4, 'x', 'asdf');
  
  
  CREATE TABLE IF NOT EXISTS `Post` (
  `id` int(11) NOT NULL auto_increment,
  `title` varchar(255) collate utf8_unicode_ci NOT NULL,
  PRIMARY KEY  (`id`)
  ) ENGINE=InnoDB  DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=7 ;
  
  INSERT INTO `Post` (`id`, `title`) VALUES
  (1, 'first post'),
  (2, 'second post'),
  (3, 'third post'),
  (4, 'fourth post'),
  (5, 'fifth post'),
  (6, 'sixth post');
  </code></pre>
  
  <p>And I want to list all posts along with a list of each username who commented on the post:</p>
  
  <pre><code>SELECT
  Post.id as post_id, Post.title as title, GROUP_CONCAT(name) 
  FROM Post 
  LEFT JOIN Comment on Comment.post_id = Post.id
  GROUP BY Post.id
  </code></pre>
  
  <p>gives me:</p>
  
  <pre><code>id  title   GROUP_CONCAT( name )
  1   first post  bill,john
  2   second post     bill
  3   third post  john
  4   fourth post     x
  5   fifth post  NULL
  6   sixth post  NULL
  </code></pre>
  
  <p>This works great, except that if a username contains a comma it will ruin the list of users. Does MySQL have a function that will let me escape these characters? (Please assume usernames can contain any characters, since this is only an example schema)</p>