Oracle - Split a record into multiple records - sql

Question

I have a schedule table for each month schedule. And this table also has days off within that month. I need a result set that will tell working days and off days for that month.
Eg.
CREATE TABLE SCHEDULE(sch_yyyymm varchar2(6), sch varchar2(20), sch_start_date date, sch_end_date date);
INSERT INTO SCHEDULE VALUES('201703','Working Days', to_date('03/01/2017','mm/dd/yyyy'), to_date('03/31/2017','mm/dd/yyyy'));
INSERT INTO SCHEDULE VALUES('201703','Off Day', to_date('03/05/2017','mm/dd/yyyy'), to_date('03/07/2017','mm/dd/yyyy'));
INSERT INTO SCHEDULE VALUES('201703','off Days', to_date('03/08/2017','mm/dd/yyyy'), to_date('03/10/2017','mm/dd/yyyy'));
INSERT INTO SCHEDULE VALUES('201703','off Days', to_date('03/15/2017','mm/dd/yyyy'), to_date('03/15/2017','mm/dd/yyyy'));
Using SQL or PL/SQL I need to split the record with Working Days and Off Days.
From above records I need result set as:
201703 Working Days 03/01/2017 - 03/04/2017
201703 Off Days 03/05/2017 - 03/10/2017
201703 Working Days 03/11/2017 - 03/14/2017
201703 Off Days 03/15/2017 - 03/15/2017
201703 Working Days 03/16/2017 - 03/31/2017
Thank You for your help.

Answer 1

Edit: I've had a bit more of a think, and this approach works fine for your insert records above - however, it misses records where there are not continuous "off day" periods. I need to have a bit more of a think and will then make some changes
I've put together a test using the lead and lag functions and a self join.
The upshot is you self-join the "Off Days" onto the existing tables to find the overlaps. Then calculate the start/end dates on either side of each record. A bit of logic then lets us work out which date to use as the final start/end dates.
SQL fiddle here - I used Postgres as the Oracle function wasn't working but it should translate ok.
select sch,
/* Work out which date to use as this record's Start date */
case when prev_end_date is null then sch_start_date
else off_end_date + 1
end as final_start_date,
/* Work out which date to use as this record's end date */
case when next_start_date is null then sch_end_date
when next_start_date is not null and prev_end_date is not null then next_start_date - 1
else off_start_date - 1
end as final_end_date
from (
select a.*,
b.*,
/* Get the start/end dates for the records on either side of each working day record */
lead( b.off_start_date ) over( partition by a.sch_start_date order by b.off_start_date ) as next_start_date,
lag( b.off_end_date ) over( partition by a.sch_start_date order by b.off_start_date ) as prev_end_date
from (
/* Get all schedule records */
select sch,
sch_start_date,
sch_end_date
from schedule
) as a
left join
(
/* Get all non-working day schedule records */
select sch as off_sch,
sch_start_date as off_start_date,
sch_end_date as off_end_date
from schedule
where sch <> 'Working Days'
) as b
/* Join on "Off Days" that overlap "Working Days" */
on a.sch_start_date <= b.off_end_date
and a.sch_end_date >= b.off_start_date
and a.sch <> b.off_sch
) as c
order by final_start_date

Answer 2

If you had a dates table this would have been easier.
You can construct a dates table using a recursive cte and join on to it. Then use the difference of row number approach to classify rows with same schedules on consecutive dates into one group and then get the min and max of each group which would be the start and end dates for a given sch. I assume there are only 2 sch values Working Days and Off Day.
with dates(dt) as (select date '2017-03-01' from dual
union all
select dt+1 from dates where dt < date '2017-03-31')
,groups as (select sch_yyyymm,dt,sch,
row_number() over(partition by sch_yyyymm order by dt)
- row_number() over(partition by sch_yyyymm,sch order by dt) as grp
from (select s.sch_yyyymm,d.dt,
/*This condition is to avoid a given date with 2 sch values, as 03-01-2017 - 03-31-2017 are working days
on one row and there is an Off Day status for some of these days.
In such cases Off Day would be picked up as sch*/
case when count(*) over(partition by d.dt) > 1 then min(s.sch) over(partition by d.dt) else s.sch end as sch
from dates d
join schedule s on d.dt >= s.sch_start_date and d.dt <= s.sch_end_date
) t
)
select sch_yyyymm,sch,min(dt) as start_date,max(dt) as end_date
from groups
group by sch_yyyymm,sch,grp
I couldn't get the recursive cte running in Oracle. Here is a demo using SQL Server.
Sample Demo in SQL Server