title: How to select unique records by SQL
body: <p>When I perform <code>SELECT * FROM table</code> I got results like below:</p>
  <pre><code>1 item1 data1
  2 item1 data2
  3 item2 data3
  4 item3 data4
  </code></pre>
  <p>As you can see, there are dup records from column2 (item1 are dupped). So how could I just get result like this:</p>
  <pre><code>1 item1 data1
  2 item2 data3
  3 item3 data4
  </code></pre>
  <p>Only one record are returned from the duplicate, along with the rest of the unique records.</p>