title: If an UNION doesn't contain the same column I can't use it?
body: <p>I read this online:</p>
  
  <p>Each query in a <code>UNION</code> must contain the same columns, expressions, or aggregate functions, and they must be listed in the same order.</p>
  
  <p>If this saying if I have a query for example </p>
  
  <pre><code>SELECT   TOP (1) WITH TIES employee_id, SUM(stars) AS 'total'
  FROM     Table_A
  GROUP BY employee_id
  ORDER BY 'total' DESC
  </code></pre>
  
  <p>I can't use <code>UNION</code> to get from a different <code>table_B</code> the name of the employee that <code>TABLE_A</code> doesn't have. 
  <code>Table_B</code> share the <code>employee_id</code> is just call differently <code>emp_id</code> and I would like to output the name of the employee which only <code>TABLE_B</code> has <code>emp_namefirst</code>, <code>emp_namelast</code>.</p>