title: mysql update one field, replace first character
body: <p>I have a table name <code>tariff</code>, but now I want to replace values in column <code>service_code</code></p>
  
  <p>The values are like this:</p>
  
  <pre><code>D2P
  D2D
  D2D
  D2P
  D2D
  </code></pre>
  
  <p>What I want to achieve:</p>
  
  <pre><code>P2P
  P2D
  P2D
  P2P
  P2D
  </code></pre>
  
  <p>Just changing the 'D' to 'P' as first character</p>