Question for analytic functions experts

Question

Hi,
I have an ugly table containing an implicit master detail relation.
The table can be ordered by sequence and then each detail is beneath it's master (in sequence).
If it is a detail, the master column is NULL and vice versa.
Sample:
SEQUENCE MASTER DETAIL BOTH_PRIMARY_KEYS
1____________A______________1
2___________________A_______1
3___________________B_______2
4____________B______________2
5___________________A_______3
6___________________B_______4
Task: Go into the table with the primary key of my detail, and search the primary key of it's master.
I already have a solution how to get it, but I would like to know if there is an analytic statement,
which is more elegant, instead of selfreferencing my table three times. Somebody used to analytic functions?
Thanks,
Dirk

Answer 1

Hi,
Do you mean like this?
with data as (
select 1 sequence, 'A' master, null detail, 1 both_primary_keys from dual union all
select 2, null, 'A', 1 from dual union all
select 3, null, 'B', 2 from dual union all
select 4, 'B', null, 2 from dual union all
select 5, null, 'A', 3 from dual union all
select 6, null, 'B', 4 from dual )
select (select max(both_primary_keys) keep (dense_rank last order by sequence)
        from data
        where sequence < detail_record.sequence and detail is null) master_primary_key
from data detail_record
where (both_primary_keys=3 /*lookup detail key 3 */  and master is null)