title: Rename a select column in sql
body: <p>I have a question about SQL. Here is the case:
  I have a table with 5 columns (C1...C5)
  I want to do</p>
  
  <pre><code> select (C1+C2*3-C3*5/C4) from table;
  </code></pre>
  
  <p>Is there any way of naming the resulting column for referring later in a query ?</p>