select id,count(*)
from (
    select id from T1
    union all
    select id from T2
    union all
    select id from T3
    union all
    select id from T4
    union all
    select id from T5
) as t
group by id
having id>1

(
SELECT T1.id
FROM T1,T2
WHERE T1.id=T2.id
)
union
(
SELECT T1.id
FROM T1,T3
WHERE T1.id=T3.id
)
union
(SELECT T1.id
FROM T1,T4
WHERE T1.id=T4.id
)
union
(SELECT T1.id
FROM T1,T5
WHERE T1.id=T5.id
)
union
(SELECT T2.id
FROM T2,T3
WHERE T2.id=T3.id
)
union
(SELECT T2.id
FROM T2,T4
WHERE T2.id=T4.id
)
union
(SELECT T2.id
FROM T2,T5
WHERE T2.id=T5.id
)
union
(SELECT T3.id
FROM T3,T4
WHERE T3.id=T4.id
)
union
(SELECT T3.id
FROM T3,T5
WHERE T3.id=T5.id
)
union
(SELECT T4.id
FROM T4,T5
WHERE T4.id=T5.id
)

select id,count(*)
from (
    select id from T1
    union all
    select id from T2
    union all
    select id from T3
    union all
    select id from T4
    union all
    select id from T5
) as t
group by id
having count(*)>1

create type A(a,b);
create function B() returns setof A as
declare
ret A;
begin
for ret in select c,d from C
loop
return next ret;
end loop;
for ret in select e,f from E
loop
return next ret;
end loop;
end;