Summarizing redundant SQL information - sql

Question

Given (Oracle 11g):
MANUFACTURER
------------
ID
NAME
CARS
---------
CAR_ID
MANUFACTURER_ID
NAME
PARTS
---------
PART_ID
CAR_ID
PART_NAME
Is it possible from SQL to get a listing of parts by car and manufacturer in a single query without repeating the redundant data on each row?
Something like:
FORD ESCORT Windshield Wiper
Horn
Steering Wheel
F-150 Windshield Wiper
Horn
Bed Liner
TOYOTA CAMRY Floor Mat
Door Handle
CIVIC Headlight
Horn
Or does something like this require application-level logic and/or use of reporting features. I've tried numerous queries, but gotten nothing close thus far.

Answer 1

Try the lag function like this:
WITH manufacturer AS (
SELECT 1 manufacturer_id, 'FORD' NAME FROM dual
UNION ALL SELECT 2, 'TOYOTA' FROM dual)
, CAR AS (
SELECT 1 car_id, 1 manufacturer_id, 'ESCORT' AS name FROM dual
UNION ALL SELECT 2, 1, 'F-150' FROM dual
UNION ALL SELECT 3, 2, 'CAMRY' FROM dual
UNION ALL SELECT 4, 2, 'CIVIC' FROM dual)
, part AS (
SELECT 1 AS part_id, 1 AS car_id, 'Windshield Wiper' AS part_name FROM dual
UNION ALL SELECT 2, 1, 'Horn' FROM dual
UNION ALL SELECT 3, 1, 'Steering Wheel' FROM dual
UNION ALL SELECT 4, 2, 'Windshield Wiper' FROM dual
UNION ALL SELECT 5, 2, 'Horn' FROM dual
UNION ALL SELECT 6, 2, 'Bed Liner' FROM dual
UNION ALL SELECT 7, 3, 'Floor Mat' FROM dual
UNION ALL SELECT 8, 3, 'Door Handle' FROM dual
UNION ALL SELECT 9, 4, 'Headlight' FROM dual
UNION ALL SELECT 10, 4, 'Horn' FROM dual)
SELECT case lag (m.name) over (order by p.part_id)
when m.name then null
else m.name
end as manufcturer,
case lag (c.name) over (order by p.part_id)
when c.name then null
else c.name
end as carname,
p.part_name
FROM manufacturer m INNER JOIN car c ON m.manufacturer_id = c.manufacturer_id
INNER JOIN part p ON p.car_id = c.car_ID
;
OUTPUT:
MANUFACTURER CARNAME PART_NAME
------------- --------- -----------------
FORD ESCORT Windshield Wiper
Horn
Steering Wheel
F-150 Windshield Wiper
Horn
Bed Liner
TOYOTA CAMRY Floor Mat
Door Handle
CIVIC Headlight
Horn

Answer 2

The natural way to get the result is:
select m.name as manufacturer_name, c.name as car_name, p.name as part_name
from manufacturer m join
cars c
on c.manufacturer_id = m.id join
parts p
on p.car_id = c.car_id;
This will be in a format where all the cells are filled in the table (so 'Ford' will be in the first few rows of the table).
If you only want the first appearance of each name, you can use row_number() (and be sure to sort the results in the end):
select (case when m_seqnum = 1 then manufacturer_name else '' end) as manufacturer_name,
(case when c_seqnum = 1 then car_name else '' end) as car_name,
part_name
from (select m.name as manufacturer_name, c.name as car_name, p.name as part_name,
row_number() over (partition by m.name order by c.name, p.name) as m_seqnum,
row_number() over (partition by m.name, c.name order by p.name) as c_seqnum
from manufacturer m join
cars c
on c.manufacturer_id = m.id join
parts p
on p.car_id = c.car_id
) mcp
order by manufacturer_name, car_name, part_name;