Help with a really simple SQL statement

Question

Hi All
I'm relatively new to SQL and can't get my head round what I believe to be a really simple problem.
I have a table I want to query called locations. We use locations to mean groups and regions as well as people s ofr example:
TABLE: LOCATION
IDENTIFIER----------NAME-----------------PART_OF
101--------------------USER A---------------123
123--------------------GROUP A-------------124
etc
What I'm trying to write is a statement that will return the 'PART_OF' as the 'NAME' rather than the ID number if the ID = 101.
I was wondering if a nested select statement would do (select as select etc) but just can't get my head round it!
Any ideas?
TIA. Jake.

Answer 1

Hi Jake,
It's not clear what you are looking for. If USER A is just Part of GROUP A, a self-join will do:
SQL> with loc as (select 101 locid, 'USER A' locname, 123 part_of from dual
             union all
             select 123 locid, 'GROUP A' locname, 124 part_of from dual
             union all
             select 124 locid, 'REGION A' locname, null part_of from dual)
-- End of test data
select l1.locid, l1.locname, l2.locname part_of
  from loc l1, loc l2
where l2.locid(+) = l1.part_of
     LOCID LOCNAME  PART_OF
       101 USER A   GROUP A
       123 GROUP A  REGION A
       124 REGION A        
3 rows selected.But if you want USER A to be part of REGION A, then you need a hierarchia lquery:
SQL> with loc as (select 101 locid, 'USER A' locname, 123 part_of from dual
             union all
             select 123 locid, 'GROUP A' locname, 124 part_of from dual
             union all
             select 124 locid, 'REGION A' locname, null part_of from dual)
-- End of test data
select l1.locid, l1.locname, connect_by_root(locname) part_of
  from loc l1
start with part_of is null
connect by prior locid = part_of
     LOCID LOCNAME  PART_OF
       124 REGION A REGION A
       123 GROUP A  REGION A
       101 USER A   REGION A
3 rows selected.Regards
Peter