title: Simple Percentage Column in SQL
body: <p>I am relatively new to SQL and looking to pick up a few simple tricks. I have managed to create a query that selects each different type of car permit (<em>chargeType</em>), counts the number issued for each one (<em>num</em>), and adds a column that shows the total number of permits issued (<em>total</em>). The code is below.</p>
  
  <pre><code>SELECT chargeType, 
         COUNT(chargeType) AS num,
         (SELECT COUNT(chargeType) 
         FROM permit) AS total
  FROM permit
  GROUP BY chargeType
  </code></pre>
  
  <p>I now want to add a final column which shows the percentage of each permit type issued. So the number of each permit type divided by the total multiplied by 100, but I am struggling to do it. Can anybody help?</p>