title: MySQL explain Query understanding
body: <p>I've read on some blogs and in some articles related to optimization, how to optimize queries. I read I need to use indexes and make sure all my primary key and foreign keys are set correctly using a good relational database schema.</p>
  
  <p>Now I have a query I need to optimize and I get this on the <code>EXPLAIN</code>:</p>
  
  <pre><code>Using where; Using temporary; Using filesort
  </code></pre>
  
  <p>I am using MySQL 5.5</p>
  
  <p>I know I am using <code>WHERE</code> but not with my temporary table nor filesort? What does this mean? </p>