st: How to search in a large database the id of patients whos medication is revised

[Muhammad Riaz <riaz_stata@live.co.uk>]

 Dear Stata list,
 
I would be grateful if somebody could give me a syntax for a command  to look at the id whether any patients have received a the same or different prescription. 
 
A patient gets prescription for medication, the medication could be one of (say A, B, C) for the same disease. the patients prescription might be revised may be with old medication or any other out of the three (A, B, C) at another date. Just to make it clear that the prescription is not revised for all patients but revised for some of them. I want to search the ids of patients whose prescription is revised and to see whether it is revised with the same medication or any other out of three (A, B, C). the database look like as below 
 
for example medication (A) is revised for id=100002120 at date 23-Dec-09 and 28-Feb-10. I need run pick up these repeated ids and see there medication whether it is the same or different.
 
Riaz
  		 	   		  
_________________________________________________________________
http://clk.atdmt.com/UKM/go/197222280/direct/01/
Do you have a story that started on Hotmail? Tell us now
*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/