title: Replace substring using REGEXP in MYSQL
body: <p>In my forum I have a BB code to display youtube videos.
  following options can be used to extract youtube video code and use this code to build the embed code:</p>
  
  <pre><code>[youtube]http://www.youtube.com/watch?v=_OBlgSz8sSM&amp;feature=related[/youtube]
  [youtube]http://www.youtube.com/watch?v=_OBlgSz8sSM[/youtube]
  [youtube]_OBlgSz8sSM[/youtube]
  </code></pre>
  
  <p>All these options return the youtube video code __OBlgSz8sSM</p>
  
  <p>After upgrade to new version of forum the first two options with parsing of youtube link not working and only the last option with [youtube]_OBlgSz8sSM[/youtube] is work.</p>
  
  <p>These BB codes are part of forum posts and not in separate field in database.</p>
  
  <p>My goal is to replace all sub strings that start with [youtube] AND end with [/youtube] that contain ?v= with </p>
  
  <pre><code>[youtube]11 characters from ?v=[/youtube]
  </code></pre>
  
  <p>I am using MySQL
  table name is POST
  field name that contain these BB codes is PAGETEXT</p>
  
  <p>Can you please assist me to build this update. </p>