Pl/SQL - Extract text and combine if duplicates - plsql

Question

Oracle 10g
My requirements are to:
Select each department
Select each individual item per department (each item get's its own row, but combine if duplicates)
Select each color per distinct department AND item (if duplicate, select the lowest number)
Select each user per distinct department AND item (aggregate if multiple)
DB data
Department Item_List Color User
Research Item 1 1. Blue John
Research Item 1;Item 2 2. Blue Mike
Research Item 1;Item 2; Item 3 1. Red Steve
Research Item 2 1. Purple John
Research Item 1;Item 4 2. Red Bill
Ops Item 1;Item 2 3. Silver John
Ops Item 1;Item 3 3. Silver Mike
Ops Item 4 4. Yellow Mark
Expected Results
Department Item_List Color User
Research Item 1 1. Blue John, Mike
Research Item 2 1. Blue Mike
Research Item 1 1. Red Steve, Bill
Research Item 2 1. Red Steve
Research Item 3 1. Red Steve
Research Item 2 1. Purple John
Research Item 4 1. Red Bill
Ops Item 1 3. Silver John, Mike
Ops Item 2 3. Silver John
Ops Item 3 3 Silver Mike
Ops Item 4 4. Yellow Mark
I am using the following SQL, but it is not working:
with data as
(
select
DEPARTMENT,
ITEM_LIST,
(length(ITEM_LIST)-length(replace(ITEM_LIST,';','')))+1 cnt,
MIN(Color) as Color,
wm_concat(USER) as USER
from DataBase_Table
Group by
DEPARTMENT,
ITEM_LIST
)
select
DEPARTMENT
ITEM_LIST,
Color,
User
from
(
select distinct
DEPARTMENT,
ltrim(regexp_substr(ITEM_LIST,'[^;]+',1,level)) ITEM_LIST,
Color,
level,
User
from data
connect by level <= cnt
order by DEPARTMENT
)
;

Answer 1

with
t1 as (
select
department,
trim(regexp_substr(item_list, '[^;]+', 1, occ)) as item,
to_number(regexp_substr(color, '^\d+')) as color_no,
regexp_replace(color, '^\d+(.*)$', '\1') as color_name,
user_
from
(
select level as occ from dual
connect by level <= (select max(length(item_list)) from source)
),
source
where regexp_substr(item_list, '[^;]+', 1, occ) is not null
)
select
department,
item,
color,
listagg(user_, ',') within group (order by user_)
from
(
select
min(color_no)||color_name as color,
color_name
from t1
group by color_name
)
natural join t1
group by
department,
item,
color
order by 1 desc, 2, 3
SQLFiddle
In Oracle 10 you should use
wm_concat(distinct user_)
instead of
listagg(user_, ',') within group (order by user_)