PostgreSQL 从多个表中删除外部连接的行

Question

I am trying to delete rows from table where theire IDs doesnt exist in other 2 tales. on PostgreSQL:

table A:

idB	idC	age
1	4	Three
2	5	Three
3	6	Three

table B:

idB	name	age
3	Two	Three
7	Two	Three

table C:

idC	name	age
4	Two	Three
5	Two	Three
6	Two	Three

final table A:

idB	idC	age
3	6	Three

---

first row of table A should be deleted because idC = 4 doesnt exist in table C Second row of table A should be deleted because idB = 2 doesnt exist in table B Third row of table A should be kept idB = 3 exists in table B and idC = 6 exists in table C

How can I do that?

Answer 1

here is how you can do it:

with tt as (
  select a.* from tableA a
  left join tableB b on a.idb =b.idb
  left join tableC c on a.idC = c.idc
  where b.idb is null or c.idc is null
)
delete from tableA a
using tt 
where a.idB = tt.idB
and a.idC = tt.idC

Answer 2

Simply use not exists :

delete from tableA a
    where not exists (select 1 from tableB b where b.idB = a.idB) or
          not exists (select 1 from tableC c where c.idC = a.idC);