title: reading next observation's value in current observation
body: <p>I've a dataset called 'input' with the following observations</p>
  
  <p>ID  Salary<br>
  10  1000<br>
  20  2000<br>
  30  3000<br>
  40  4000</p>
  
  <p>I need an output dataset with following observations</p>
  
  <p>ID Salary Next_row_Salary<br>
  10 1000   2000<br>
  20 2000   3000<br>
  30 3000   4000<br>
  40 4000   null  </p>
  
  <p>Note: The scenario is next obersavtion's salary should be the current observation's value for the column Next_Row_salary.
  If there is no next observation then the current observation's value for the column Next_Row_salary should be 'null'.</p>
  
  <p>Kindly help me out in creating a sas code for this scenario.</p>