Test for the Absence of Duplicate Tuples

1. The unique construct returns true if the argument subquery contains no duplicate tuples.
2. Find all customers who have only one account at the SFU branch.

    aaaaa aa ¯select T.cname
   
   		 from depositor as T
   
   		 where unique (select R.cname
   
   		 		 		 		 		 from account, depositor as R
   
   		 		 		 		 		 where T.cname = R.cname and
   
   		 		 		 		 		 		 		 R.account# = account.account# and
   account.bname = ``SFU")