Os comandos SQL

create table R (a int, b int)
create table S (c int, d int)
insert into R values(1,2)
insert into R values(2,3)
insert into R values (2,3)
insert into R values (3,5)
insert into R values (4,1)
insert into S values (1,2)
insert into S values (2,1)
insert into S values (2,3)
insert into S values (3,5)
select r.a, r.b from R
  where not exists
    (select * from S where s.c=r.a and s.d=r.b)

Produzem um resultado que, além da linha de títulos, contém: