title: Combining SQL queries without JOIN or UNION
body: <p>I need to count rows in two tables, and I would like to make a single SQL-query do the job. After some research I found an solution which I modified to this:</p>
  
  <pre><code>SELECT COUNT(activate_account.id), COUNT(members.id) FROM members, activate_account 
  WHERE members.email = :email or activate_account.email = :email
  </code></pre>
  
  <p>Now my question is: is this a good way to combine two SELECT queries, is this just as good solution as if I would have used JOIN or UNION (meaning should there be any peformance improvement compared to if I would have two separate SELECT queries)?</p>