Observe o resultado de uma consulta mostrado a seguir.
O comando SQL que NÃO produz o resultado acima é:
select x.*
from x
where not exists (select * from z where z.a=x.a)
union all
select y.*
from y
where not exists (select * from z where z.c=y.c)
select 6 a, 3 b
union
select y.*
from y
where not exists (select * from z where z.c=y.c)
select x.*
from x
where not exists (select * from z where z.a=x.a)
select x.*
from x
where not exists (select * from z where z.a=x.a)
union select 6,3
select x.*
from x
where not exists (select * from z where z.a=x.a)
union all
select 6,3