title: MySQL update content if exists
body: <p>Ok, so I know there are some questions similar, but how would I update a table like this in MySQL:</p>
  
  <pre><code>+----+----------+---------+-------------------------+
  | id | username | subject | content                 |
  +----+----------+---------+-------------------------+
  | 1  | Fred     | English | Lorem Ipsum             |
  +----+----------+---------+-------------------------+
  </code></pre>
  
  <p>So lets say, i want to update the content in the users English book, however, I want to insert it if it is not already in there, and then in te future update it.</p>