title: Wrapping SQL query in parentheses causes syntax error
body: <p>The following query works:</p>
  
  <pre><code>SELECT DISTINCT `number`
     FROM `employee`
     WHERE `number` IN
              (SELECT `department_manager`
               FROM `department`)
     UNION
       (SELECT DISTINCT `manager`
        FROM `employee`
        WHERE `manager` IS NOT NULL)
  </code></pre>
  
  <p>But as soon as I wrap the query with parentheses it doesn't work anymore:</p>
  
  <pre><code> (SELECT DISTINCT `number`
     FROM `employee`
     WHERE `number` IN
              (SELECT `department_manager`
               FROM `department`)
     UNION
       (SELECT DISTINCT `manager`
        FROM `employee`
        WHERE `manager` IS NOT NULL))
  </code></pre>
  
  <p>Causing syntax error:</p>
  
  <pre><code>ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'UNION
  </code></pre>
  
  <p>Wrapping other select queries in parentheses doesn't cause problems, this works for example:</p>
  
  <pre><code>(SELECT DISTINCT number FROM johnson.employee);
  </code></pre>
  
  <p>What is the difference between these?</p>