title: MySQL Calculate Percentage
body: <p>I have a MySQL database with 4 items: <code>id</code> (numerical), <code>group_name</code>, <code>employees</code>, and <code>surveys</code>.</p>
  
  <p>In my <code>SELECT</code> I need to calculate the percentage of 'employees' who, by the number in 'surveys', have taken the survey.</p>
  
  <p>This is the statement I have now:</p>
  
  <pre><code>SELECT
    group_name,
    employees,
    surveys,
    COUNT( surveys ) AS test1, 
    ((COUNT( * ) / ( SELECT COUNT( * ) FROM a_test)) * 100 ) AS percentage
  FROM
    a_test
  GROUP BY
    employees
  </code></pre>
  
  <p>Here is the table as it stands: </p>
  
  <pre><code>INSERT INTO a_test (id, group_name, employees, surveys) VALUES
  (1, 'Awesome Group A', '100', '0'),
  (2, 'Awesome Group B', '200', '190'),
  (3, 'Awesome Group C', '300', '290');
  </code></pre>
  
  <p>I would love to calculate the percentage of <code>employees</code> who by the number in <code>surveys</code> have taken the survey. i.e. as shown in the data above, the <code>Awesome Group A</code> would be 0% and <code>Awesome Group B</code> would be 95%.</p>