PostgreSQL two groups segregated but not ordered only by zero price column - postgresql

Question

I need help with a bit of a crazy single-query goal please that I'm not sure if GROUP BY or sub-SELECT applies to?
The following query:
SELECT id_finish, description, inside_rate, outside_material, id_part, id_metal
FROM parts_finishing AS pf
LEFT JOIN parts_finishing_descriptions AS fd ON (pf.id_description=fd.id);
Returns the results like the following:
+-------------+-------------+------------------+--------------------------------+
| description | inside_rate | outside_material | id_part - id_finish - id_metal |
+-------------+-------------+------------------+--------------------------------+
| Nickle | 0 | 33.44 | 4444-44-44, 5555-55-55 |
+-------------+-------------+------------------+--------------------------------+
| Bend | 11.22 | 0 | 1111-11-11 |
+-------------+-------------+------------------+--------------------------------+
| Pack | 22.33 | 0 | 2222-22-22, 3333-33-33 |
+-------------+-------------+------------------+--------------------------------+
| Zinc | 0 | 44.55 | 6000-66-66 |
+-------------+-------------+------------------+--------------------------------+
I need the results to return in the fashion below but there are catches:
I need to group by either the inside_rate column or the outside_material column but ORDER BY the description column but not ORDER BY or sort them by price (inside_rate and outside_material are the prices). So we know that they belong to a group if inside_rate is 0 or to the other group if outside_material is 0.
I need to ORDER BY the description column desc secondary after they are returned per group.
I need to return a list of parts (composed of three separate columns) for that inside/outside group / price for that finishing.
Stack format fix.
+-------------+-------------+------------------+--------------------------------+
| description | inside_rate | outside_material | id_part - id_finish - id_metal |
+-------------+-------------+------------------+--------------------------------+
| Bend | 11.22 | 0 | 1111-11-11 |
+-------------+-------------+------------------+--------------------------------+
| Pack | 22.33 | 0 | 2222-22-22, 3333-33-33 |
+-------------+-------------+------------------+--------------------------------+
| Nickle | 0 | 33.44 | 4444-44-44, 5555-55-55 |
+-------------+-------------+------------------+--------------------------------+
| Zinc | 0 | 44.55 | 6000-66-66 |
+-------------+-------------+------------------+--------------------------------+
The tables I'm working with and their data types:
Table "public.parts_finishing"
Column | Type | Modifiers
------------------+---------+-------------------------------------------------------------
id | bigint | not null default nextval('parts_finishing_id_seq'::regclass)
id_part | bigint |
id_finish | bigint |
id_metal | bigint |
id_description | bigint |
date | date |
inside_hours_k | numeric |
inside_rate | numeric |
outside_material | numeric |
sort | integer |
Indexes:
"parts_finishing_pkey" PRIMARY KEY, btree (id)
Table "public.parts_finishing_descriptions"
Column | Type | Modifiers
------------+---------+------------------------------------------------------------------
id not null | bigint | default nextval('parts_finishing_descriptions_id_seq'::regclass)
date | date |
description | text |
rate_hour | numeric |
type | text |
Indexes:
"parts_finishing_descriptions_pkey" PRIMARY KEY, btree (id)
The second table's first column is just id. (Why are we still dealing with a 1024 static width layout in 2015?)
I'd make an SQL fiddle though it refuses to load for me regardless of the browser.

Answer 1

Not entirely sure I understand your question. Might look like this:
SELECT pd.description, pf.inside_rate, pf.outside_material
, concat_ws(' - ', pf.id_part::text
, pf.id_finish::text
, pf.id_metal::text) AS id_part_finish_metal
FROM parts_finishing pf
LEFT JOIN parts_finishing_descriptions fd ON pf.id_description = fd.id
ORDER BY (pf.inside_rate = 0) -- 1. sorts group "inside_rate" first
, pd.description DESC NULLS LAST -- 2. possible NULL values last
;