title: Unsupported SubQuery Expression : Correlating expression cannot contain unqualified column references
body: <p>In <code>Hive</code> the following query fails :</p>
  
  <pre><code>  Select a,b,c from t1 where a in (0,100) AND b in (select b from t2
    where d&gt;2 GROUP BY 1 ) LIMIT 1;
  </code></pre>
  
  <p>Schema :  </p>
  
  <pre><code>t1(a,b,c)
  t2(b,d,e)
  </code></pre>
  
  <p>Error log : </p>
  
  <blockquote>
    <p>Unsupported SubQuery Expression 'b': Correlating expression cannot
    contain unqualified column references.</p>
  </blockquote>
  
  <p>What is correlating expression? what are unqualified column references ? and can you generalize the error here ..</p>