title: Avoiding Nested Queries
body: <p>How Important is it to avoid nested queries.</p>
  
  <p>I have always learnt to avoid them like a plague. But they are the most natural thing to me. When I am designing a query, the first thing I write is a nested query. Then I convert it to joins,  which sometimes takes a lot of time to get right. And rarely gives a big performance improvement (sometimes it does)</p>
  
  <p>So are they really so bad. Is there a way to use nested queries without temp tables and filesort</p>