How to count days between 2 rows multiple scenarios - sql

Question

I would like to count days from table like this:
[]]1
I have 2 columns with status and date, I need to count how many days one row had status with 1 and 3, for example: first row has staus 1 second row has status 2 the difference between those two rows is 3 days, the same eight and nine row. All those calculation I neet to do in sql.

Answer 1

This will work for sql-server 2012. I was unable to find any documentation that would prevent this syntax in express.
DECLARE #t table(Status int, Date datetime)
INSERT #t
VALUES
(1,'2018-02-15'),
(2,'2018-02-18'),
(3,'2018-02-20'),
(2,'2018-02-23')
;WITH CTE as
(
SELECT Date, lead(Date)over(order by date) NextDate, Status
FROM #t
)
SELECT sum(DateDiff(day, Date, NextDate))
FROM CTE
WHERE Status in (1,3)

Answer 2

You can do that if you have analytic (aka window) functions available (Oracle, SQL Server, Postgresql, MySQL). The basic idea would be (using Oracle SQL dialect):
select
sum(trunc(next_date) - trunc(dat))
from (
select
status,
dat,
lead(dat) over (order by dat asc) next_date
from
( -- This is a "fake" data table
select 1 as status, to_date('15/2/2018' ,'dd/mm/yyyy') dat from dual
union all
select 2 as status, to_date('18/2/2018' ,'dd/mm/yyyy') dat from dual
union all
select 3 as status, to_date('20/2/2018' ,'dd/mm/yyyy') dat from dual
union all
select 2 as status, to_date('23/2/2018' ,'dd/mm/yyyy') dat from dual
union all
select 4 as status, to_date('24/2/2018' ,'dd/mm/yyyy') dat from dual
union all
select 7 as status, to_date('27/2/2018' ,'dd/mm/yyyy') dat from dual
union all
select 9 as status, to_date('28/2/2018' ,'dd/mm/yyyy') dat from dual
union all
select 3 as status, to_date('1/3/2018' ,'dd/mm/yyyy') dat from dual
union all
select 14 as status, to_date('4/3/2018' ,'dd/mm/yyyy') dat from dual
union all
select 15 as status, to_date('7/3/2018' ,'dd/mm/yyyy') dat from dual
union all
select 1 as status, to_date('10/3/2018' ,'dd/mm/yyyy') dat from dual
union all
select 2 as status, to_date('14/3/2018' ,'dd/mm/yyyy') dat from dual
) d
) d2
where
status in (1, 3);
Other dialects may be slightly different but the idea is the same.