The below API demonstrates two update queries. As update queries do not return any meaniful information, below API uses Text tag to 

send back the feedback submitted.

<?xml version="1.0" encoding="UTF-8" ?>
<Resource xmlns="http://xml.metamug.net/resource/1.0" v="1.0">
	<Request method="POST">
	    <Param name="source" type="text" value="feedback"/>
	    <Sql id="addFeedback" type="update">
          INSERT into feedback (name,email,issue,description) VALUES 
          ($name,$email,$issue,$description) 
      	</Sql>
      	<Sql id="addUser" type="update"> 
          	INSERT IGNORE INTO feedback_user(emailUsers,registration_source) VALUES ($email,$source)
      	</Sql>
      <Text id="feedback">
      	name: $name,feedback: $issue - $description
      </Text>
	</Request>
</Resource>


Inserting Duplicate Records

addUser  ignores duplicate inserts preventing the POST API from failing in case the user already exists in the table.

https://stackoverflow.com/questions/548541/insert-ignore-vs-insert-on-duplicate-key-update