title: Meaning of '0', and two apostrophes ' ' in SQL SELECT statement
body: <p>I'm trying to wrap my head around somebody else's query, and stepped into this:</p>
  
  <pre><code>SELECT '0' AS Interaction,
         a.name AS 'Serial_No',
         ' ' AS Questionnaire_ID,
  </code></pre>
  
  <p>and so on.</p>
  
  <p>Any ideas on what does '0' and ' ' (empty space between two apostrophes) mean when it comes to column names in SQL SELECT?</p>