title: Invalid identifier when use alternate name of column
body: <p>I have some lines of code, but it won't work somehow. I want to call this column round() the name &quot;Diem&quot; to use  it later, but Diem &gt;= 1 make it invalid identifier. Can somebody please help?</p>
  <pre><code>select id, name, round(avg(
  decode(grade, 'A+', 4.5,'A', 4,
  'A-',3.5, 'B+',3, 'B',2.5, 'B-', 2,
  'C+', 1.5, 'C', 1, 'C-',0.5
  )), 1) as ***DIEM***
  from takes t join student s 
  using (id)
  where tot_cred &gt;= 128
  and ***DIEM*** &gt;= 1
  group by id, name;
  </code></pre>