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Atenção
Quando referidas, considere as tabelas relacionais TX e TY, criadas e instanciadas com o script SQL a seguir.
create table TY(C int primary key not null, A int)
create table TX(A int primary key not null, B int,
foreign key (B) references TY(C)
on delete cascade
)
insert into TY values (1,0)
insert into TY(C) values (2)
insert into TY(C) values (3)
insert into TY values (5,NULL)
insert into TY values (6,NULL)
insert into TX values (1,2)
insert into TX values (2,1)
insert into TX values (3,2)
insert into TX values (4,2)