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:
