title: SQL Update, if not exist then insert
body: <p>Table Layout:</p>
  
  <pre><code>CREATE TABLE gmod_playerdata (
    dataset_id  int(255) NULL AUTO_INCREMENT,
    data_id int(255) NULL,
    option_name  varchar(100) NULL,
    option_value  varchar(100) NULL,
    PRIMARY KEY (dataset_id)
  )
  </code></pre>
  
  <p>I can't know whether the row already exists or not. <code>data_id</code> will always be filled, but can/will appear multiple times.</p>
  
  <p>I only need to update option_name and option_value, while I don't know if a option_value and option_name already exist when I run the query.</p>
  
  <p>I've read much about <code>ON DUPLICATE KEY UPDATE</code> however I kinda don't get how it is meant to be used in my scenario.</p>