title: How to find the max value of every column in a table?
body: <p>I just got stucked in finding the exact query for this requirement.<br>
  I want to find the max value in every column.</p>
  
  <p>Here is an example</p>
  
  <pre><code>A B C D
  -------
  0 3 4 1
  4 1 5 3
  5 9 6 7
  7 2 1 6
  </code></pre>
  
  <p>The result should be like this:</p>
  
  <pre><code>A | B | C | D |
  --------------
  7 | 9 | 6 | 7 |
  </code></pre>
  
  <p>That would be more helpful if you could help me out?</p>