SQL logic for Decompression - sql

Question

RDW (Retake Data Warehouse) used to reduce data volume by compression logic. Compression refers to storing physical data that only reflects changes to the underlying data source.
Inventory fact table store data in following form.
Week Item Location stock_on_hand
--------------------------------------------------
201601 I1 L1 50
201602 I1 L1 30
201605 I1 L1 60
201608 I1 L1 50
But I need sql query to get following result
Week Item Location stock_on_hand
--------------------------------------------------
201601 I1 L1 50
201602 I1 L1 30
201603 I1 L1 30
201604 I1 L1 30
201605 I1 L1 60
201606 I1 L1 60
201607 I1 L1 60
201608 I1 L1 50

Answer 1

Test data(I add several rows for better understanding and split year and week columns)
with t(year, Week , Item, Location, stock_on_hand) as
(select 2016, 01, 'I1', 'L1', 50 from dual union all
select 2016, 02, 'I1', 'L1', 30 from dual union all
select 2016 ,05, 'I1', 'L1', 60 from dual union all
select 2016 ,08, 'I1', 'L1', 50 from dual union all
select 2016, 02, 'I2', 'L1', 30 from dual union all
select 2016, 08, 'I2', 'L1', 40 from dual union all
select 2016, 02, 'I1', 'L2', 10 from dual union all
select 2016, 08, 'I1', 'L2', 40 from dual union all
select 2016, 08, 'I1', 'L3', 40 from dual)
Query
with t(year, Week , Item, Location, stock_on_hand) as
(select 2016, 01, 'I1', 'L1', 50 from dual union all
select 2016, 02, 'I1', 'L1', 30 from dual union all
select 2016 ,05, 'I1', 'L1', 60 from dual union all
select 2016 ,08, 'I1', 'L1', 50 from dual union all
select 2016, 02, 'I2', 'L1', 30 from dual union all
select 2016, 08, 'I2', 'L1', 40 from dual union all
select 2016, 02, 'I1', 'L2', 10 from dual union all
select 2016, 08, 'I1', 'L2', 40 from dual union all
select 2016, 08, 'I1', 'L3', 40 from dual),
temp(year, Week , Item, Location, stock_on_hand, ct) as(
select year, Week , Item, Location, stock_on_hand, nvl(lead(Week) over(partition by Item, Location order by year, Week)-Week,1) from t)
select year, Week + rn - 1 as week, Item, Location, stock_on_hand
from temp, xmltable('1 to xs:integer($ct)' passing ct as "ct" columns rn number path '.')
order by Item, Location ,year, week
This approach also have one minor. If you have interval in different year. Ex
select 2016, 01, 'I1', 'L1', 50 from dual union all
select 2017, 02, 'I1', 'L1', 30 from dual union all
Then it works incorrectly. I don't know whether you data has the same pattern. If it has then, please, add information to post or answer.
UPDATE
For intervals which lives in several years you can do follow(For startDate I choose date in international week)
with t(dateStart , Item, Location, stock_on_hand) as
(select to_date('28/12/2015', 'dd-mm-yyyy'), 'I1', 'L1', 50 from dual union all
select to_date('04/01/2016', 'dd-mm-yyyy'), 'I1', 'L1', 30 from dual union all
select to_date('25/01/2016', 'dd-mm-yyyy'), 'I1', 'L1', 60 from dual union all
select to_date('15/02/2016', 'dd-mm-yyyy'), 'I1', 'L1', 50 from dual union all
select to_date('01/01/2018', 'dd-mm-yyyy'), 'I1', 'L1', 30 from dual union all
select to_date('04/01/2016', 'dd-mm-yyyy'), 'I2', 'L1', 40 from dual union all
select to_date('15/02/2016', 'dd-mm-yyyy'), 'I2', 'L1', 10 from dual union all
select to_date('04/01/2016', 'dd-mm-yyyy'), 'I1', 'L2', 30 from dual union all
select to_date('15/02/2016', 'dd-mm-yyyy'), 'I1', 'L2', 40 from dual union all
select to_date('15/02/2016', 'dd-mm-yyyy'), 'I1', 'L3', 40 from dual),
temp(dateStart, Item, Location, stock_on_hand, ct) as(
select dateStart , Item, Location, stock_on_hand, nvl((lead(dateStart) over(partition by Item, Location order by dateStart)-dateStart)/7,1) from t)
select dateStart + (rn - 1)*7 as week, Item, Location, stock_on_hand
from temp, xmltable('1 to xs:integer($ct)' passing ct as "ct" columns rn number path '.')
order by Item, Location , dateStart