title: Getting percentage from group by query
body: <p>I have a problem with my SQL. I created this query:</p>
  
  <p>I don't know how can I get that result with one query. I know that to calculate percentage I have to multiply the value obtained in the counter by 100 and divide by the sum of the whole count. Can you help me?</p>
  
  <p>Many thanks.</p>