I want to insert all user and friendlink in friend_list table into friend_req but i only want to insert it if the friendlink is not in the profilelink field in the friend_req table

Another words i dont want duplication.


PHP Code:
INSERT
  INTO friend_req
     
(user,
     
profilelink
     
)
     
SELECT user,
       
friendlink
  FROM friend_list
  
 WHERE 
....................