title: Calculate the difference between results of two count(*) queries based on 2 tables in PostgreSQL
body: <p>I want to calculate the difference between the results of 2 <code>count(*)</code>-type SELECT queries executed on 2 separate tables of my PostgreSQL database.</p>
  
  <p>This what I'm currently using (however I should be able to wrap it all up into a single SELECT statement):</p>
  
  <pre><code>SELECT "count"(*) AS val1 FROM tab1;
  SELECT "count"(*) AS val2 FROM tab2;
  SELECT val2-val1;
  </code></pre>
  
  <p>Thanks in advance</p>