computer_id field in sem_computer table

Hi,

   I have a bit doubt on field computer_id in sem_computer table. Actually , I ran following query in SEPM database:

  select computer_name from sem_computer where computer_id = (select computer_id from sem_client where computer_name = 'AAA')

   The output above query gives is 'BBB'. This is quite surprising because ideally it should come as 'AAA' only ( assuming computer_id should be unique). 

   Can anybody suggest something about this problem? 

Tabish