create table rc_document (rc_document_id int, document_id int, rc_document_group_id int)\\
insert into rc_document values (1,1,1)\\
insert into rc_document values (2,2,1)\\
insert into rc_document values (3,3,1)\\
insert into rc_document values (4,4,1)\\
insert into rc_document values (5,1,2)\\
insert into rc_document values (6,3,2)\\
create table rc_document_group (rc_document_group_id int, priority int)\\
insert into rc_document_group values (1,1)\\
insert into rc_document_group values (2,2)\\
delete from rc_document
where rc_document_id not in
(
select max(d.rc_document_id) keep (dense_rank last order by dg.priority)
from rc_document d
join rc_document_group dg using (rc_document_group_id)
group by d.document_id
)\\
select * from rc_document\\
drop table rc_document\\
drop table rc_document_group\\