SQL / Scoped query

Hi,

1) How would you formulate:

SELECT UNameF,UCustomerName FROM tblUsers,tblCustomers WHERE tblUsers.ID = SESSSION[ID} AND tblCustomers.f_UserID = tblUsers.UserID

(the goal is to select all the customers of one salesperson).

2) Are PHP sessions compatible with the PHP JSON output? I don't want to show the above output merely with a $_GET parameter...