title: Select Parent and Children With MySQL
body: <p>I know this question comes up often, but today I can't find the answer I'm looking for. I have a table with this schema.</p>
  
  <pre><code>CREATE TABLE `comments` (
      `id` bigint(10) unsigned not null auto_increment,
      `parent_id` bigint(10) unsigned default 0,
      `date_sent` datetime not null,
      `content` text not null,
      PRIMARY KEY(`id`)
  ) ENGINE=InnoDB;
  </code></pre>
  
  <p>I'd like to select parent rows, and the children of those rows. I don't allow children to have children, so it's just one parent, with any number of children.</p>
  
  <p>I think I've seen this done with unions before, or inner joins.</p>