title: sql server select first row from a group
body: <p>I have table like this:</p>
  
  <pre><code>a          b
  1          23
  1          2
  1          7
  2          9
  2          11
  </code></pre>
  
  <p>I want to select the first row(order does not matter) from a "GROUP BY a" query , the result should be</p>
  
  <pre><code>a          b
  1          23
  2          9
  </code></pre>
  
  <p>I am using SQL SERVER 2008 how to write the query for this?</p>