title: SQLzoo, SELECT within SELECT tutorial
body: <p>I am currently doing this tutorial (<a href="http://sqlzoo.net/wiki/SELECT_within_SELECT_Tutorial" rel="noreferrer">http://sqlzoo.net/wiki/SELECT_within_SELECT_Tutorial</a>) and I can't answer question 8 :</p>
  
  <p><strong>Some countries have populations more than three times that of any of their neighbours (in the same continent). Give the countries and continents.</strong></p>
  
  <p>.. and my current query won't be accepted as the answer :</p>
  
  <pre><code>SELECT x.name, x.continent FROM world x
  WHERE (x.population * 3) &gt; ALL (
  SELECT y.population FROM world y
  WHERE x.continent = y.continent )
  </code></pre>
  
  <p>What am I doing wrong ? What is the answer ?</p>