title: Update statement with Replace function results zero "0" value for all rows
body: <p>I ran the following statement in our test mysql database, it works properly. However, when I ran it in production, I got all rows, including those of CLASS = 'ClassName', updated with XML value set to 0 !</p>
  
  <pre><code> UPDATE table_name c set c.XML= REPLACE (c.XML, '&lt;flag_name&gt;false&lt;/flag_name&gt;', '')
  WHERE c.CLASS = 'ClassName' 
  </code></pre>
  
  <p>I want to know the reason behind this strange behaviour?</p>
  
  <p>Note: The table structure is as follows:</p>
  
  <pre><code>CREATE TABLE `table_name` (
    `ID` int(10) unsigned NOT NULL AUTO_INCREMENT,
    `CLASS` varchar(250) NOT NULL,
    `XML` mediumtext NOT NULL,
    PRIMARY KEY (`ID`)
  ) ENGINE=InnoDB AUTO_INCREMENT=23510 DEFAULT CHARSET=utf8;
  </code></pre>
  
  <p>The expected behaviour is to remove the targeted tag </p>