SQL - creating date range - sql

Question

I am using the following follow script to show me the cap_date and max_capacity in the future and ... and sub-queries to show me the last_date and last_qty where older than the first select statement.
select
trunc(gp.cap_date) cap_date, gp.max_capacity,
(select max(trunc(gp1.cap_date))
from GPS_CAPACITY gp1
where gp.plant = gp1.plant
and gp.work_center_no = gp1.work_center_no
and gp1.cap_date = (select max(gp2.cap_date)
from GPS_CAPACITY gp2
where gp.plant = gp2.plant
and gp.work_center_no = gp2.work_center_no
and gp2.cap_date < gp.cap_date)) last_date,
(select max(gp1.max_capacity)
from GPS_CAPACITY gp1
where gp.plant = gp1.plant
and gp.work_center_no = gp1.work_center_no
and gp1.cap_date = (select max(gp2.cap_date)
from GPS_CAPACITY gp2
where gp.plant = gp2.plant
and gp.work_center_no = gp2.work_center_no
and gp2.cap_date < gp.cap_date)) last_qty
from
GPS_CAPACITY gp
where
gp.plant = 'W'
and gp.work_center_no = 'HPKG'
and trunc(gp.cap_date) > trunc(sysdate)
Output from this script looks like ...
... what I would like is to do is create a date list starting from the 'last_date' and show a qty for each date equal to last_qty; once the date list reaches the 'cap_date' qty should change to the max_capacity (the dates should run 7 days after the 'cap_date', i.e.
Any ideas?
Thanks

Answer 1

First create a cal table containing the range of dates of interest. Lets call that table cal with one column dt of type date. Assume your table above is called table_cap
Now do a
select cal.dt, case when cal.dt<cap_date then qty else max_capacity end
from cal
inner join table_cap on
(table_cap.last_date <= cal.dt
and cal.dt < adddate(capdate, interval 7 day )