title: Single Quotes in MySQL queries
body: <p>If I have a MySQL query like:</p>
  
  
  
  <pre class="lang-sql prettyprint-override"><code>SELECT this FROM that WHERE id='10'
  </code></pre>
  
  <p>and</p>
  
  <pre class="lang-sql prettyprint-override"><code>SELECT this FROM that WHERE id=10
  </code></pre>
  
  <p>both seem to work correctly.</p>
  
  <p>What is the use of the single speech marks in MySQL queries? When is it correct to use them?</p>