title: Oracle : How to delete duplicates rows when no distinct value exists?
body: <p>We have a table with many rows duplicated (2 to 4 times) (each row has the same value for each column).
  This table has 4 columns but no primary key.</p>
  
  <p>So how to delete the duplicated rows ?</p>
  
  <pre><code>Instance  status  updatetime              name
  -----------------------------------------------
  gdt546    4       2016/02/13 10:13:18     basic
  gdt546    4       2016/02/13 10:13:18     basic
  ort87a    1       2016/02/16 19:09:43     High
  ort87a    1       2016/02/16 19:09:43     High
  ort87a    1       2016/02/16 19:09:43     High
  </code></pre>
  
  <p><strong>Edited:</strong></p>
  
  <p>The output should be:</p>
  
  <pre><code> Instance  status  updatetime              name
  -----------------------------------------------
  gdt546    4       2016/02/13 10:13:18     basic
  ort87a    1       2016/02/16 19:09:43     High
  </code></pre>