SQL # of days between different date ranges - sql

Question

How can I count the number of days between a start and end date in SQL?
ID | START | END
1 |2018-1-1 |2018-1-3
2 |2018-1-1 |2018-1-4
3 |2018-1-1 |2018-1-5
Ideally would return:
DATE | COUNT
2018-1-1 | 3
2018-1-2 | 3
2018-1-3 | 3
2018-1-4 | 2
2018-1-5 | 1

Answer 1

One option is to generate all dates between min start and max end with a recursive cte and then count them.
with dates(dt1,dt2) as (select min([start]),max([end])
from tbl
union all
select dateadd(day,1,dt1),dt2
from dates
where dt1 < dt2
)
select d.dt1,count(*)
from dates d
join tbl t on d.dt1 between t.[start] and t.[end]
group by d.dt1

Answer 2

Similar approach worked out with a complete example:
DECLARE #range TABLE
(
id INT NOT NULL IDENTITY(1,1),
s_date DATETIME NOT NULL,
e_date DATETIME NOT NULL
);
INSERT INTO #range
(s_date, e_date)
VALUES
('2018-1-1','2018-1-3'),
('2018-1-1','2018-1-4'),
('2018-1-1','2018-1-5');
DECLARE #date TABLE
(
date DATETIME NOT NULL
);
INSERT INTO #date
(date)
VALUES
('2018-1-1'), ('2018-1-1'), ('2018-1-1'),
('2018-1-2'), ('2018-1-2'), ('2018-1-2'),
('2018-1-3'), ('2018-1-3'), ('2018-1-3'),
('2018-1-4'), ('2018-1-4'),
('2018-1-5');
SELECT d.date, COUNT(DISTINCT r.id)
FROM #range r
JOIN #date d ON d.date BETWEEN r.s_date AND r.e_date
GROUP BY d.date

Answer 3

I post a solution to fill gaps with a simple generator:
Check it at SQL Fiddle
MS SQL Server 2017 Schema Setup:
create table d
( ID int, fSTART date, fEND date );
insert into d values
(1, '2018-1-1' ,'2018-1-3'),
(2, '2018-1-1' ,'2018-1-4'),
(3, '2018-1-1' ,'2018-1-5');
Query 1:
;WITH Nbrs_3( n ) AS ( SELECT 1 UNION SELECT 0 ),
Nbrs_2( n ) AS ( SELECT 1 FROM Nbrs_3 n1 CROSS JOIN Nbrs_3 n2 ),
Nbrs_1( n ) AS ( SELECT 1 FROM Nbrs_2 n1 CROSS JOIN Nbrs_2 n2 ),
Nbrs_0( n ) AS ( SELECT 1 FROM Nbrs_1 n1 CROSS JOIN Nbrs_1 n2 ),
Nbrs ( n ) AS ( SELECT 1 FROM Nbrs_0 n1 CROSS JOIN Nbrs_0 n2 ),
ns (n) as (SELECT ROW_NUMBER() OVER (ORDER BY n) FROM Nbrs )
select distinct dateadd( day, n-1,fSTART )
from d inner join ns on dateadd( day, n-1, fSTART ) between fStart and fend
order by 1
Results:
| |
|------------|
| 2018-01-01 |
| 2018-01-02 |
| 2018-01-03 |
| 2018-01-04 |
| 2018-01-05 |

Answer 4

I used cross apply to get your results:
I am assuming you want to know how many times that date is between a start and end date of the other table.
Setup:
declare #s table
( ID int, fSTART date, fEND date );
insert into #s values
(1, '2018-1-1' ,'2018-1-3'),
(2, '2018-1-1' ,'2018-1-4'),
(3, '2018-1-1' ,'2018-1-5');
declare #d table
(dte date)
insert into #d
values
('1/1/2018')
,('1/2/2018')
,('1/3/2018')
,('1/4/2018')
,('1/5/2018')
The Query:
select d.dte
,ct = sum(case when d.dte between s.fstart and s.fend then 1 else 0 end)
from #d d
cross apply #s s
group by dte
results:
dte ct
2018-01-01 3
2018-01-02 3
2018-01-03 3
2018-01-04 2
2018-01-05 1