title: finding the percentage using case statement
body: <p>The following SQL Query :</p>
  
  <pre><code>SELECT 
  
  SUM(aol_int) AS AOL,
  SUM(android_phone_int) AS Android_Phone,
  SUM(androidTablet_int) AS Android_Tablet
  
  FROM mytable;
  </code></pre>
  
  <p>Is giving me the total values under AOL, Android_Phone and Android_Tablet columns</p>
  
  <p>However, I am trying to get the percentage of AOL, Android_Phone and Android_Tablet and hence I decided to write the above query as follows:</p>
  
  <pre><code>SELECT 
  
  SUM(CASE WHEN 'aol_int' THEN 100 END) / Count(aol_int) AS AOL,
  SUM(CASE WHEN ‘android_phone_int’ THEN 100 END) /Count(android_phone_int) AS Android_Phone,
  SUM(CASE WHEN ‘androidTablet_int’ THEN 100 END)/Count(androidTablet_int) AS Android_Tablet
  
  FROM mytable;
  </code></pre>
  
  <p>And I am getting NULL in each column. What am I doing wrong here?</p>