使用日期开始日期时间和结束日期时间的 SQL 查询组

Question

I have the following table Jobs :

|Id  | StartDateTime       | EndDateTime
+----+---------------------+----------------------
|1   | 2020-10-20 23:00:00 | 2020-10-21 05:00:00
|2   | 2020-10-21 10:00:00 | 2020-10-21 11:00:00

Note job id 1 spans October 20 and 21.

I am using the following query

SELECT DAY(StartDateTime), COUNT(id)
FROM Job
GROUP BY DAY(StartDateTime)

To get the following output. But the problem I am facing is that day 21 is not including job id 1. Since the job spans two days I want to include it in both days 20 and 21.

Day | TotalJobs
----+----------
20  | 1
21  | 1

I am struggling to get the following expected output:

Day | TotalJobs
----+----------
20  | 1
21  | 2

Answer 1

One method is to generate the days that you want and then count overlaps:

with days as (
      select convert(date, min(j.startdatetime)) as startd,
             convert(date, max(j.enddatetime)) as endd
      from jobs j
      union all
      select dateadd(day, 1, startd), endd
      from days
      where startd < endd
     )
select days.startd, count(j.id)
from days left join
     jobs j
     on j.startdatetime < dateadd(day, 1, startd) and
        j.enddatetime >= startd
group by days.startd;

Here is a db<>fiddle.

Answer 2

You can first group by with same start and end date and then group by for start and end date having different start and end date

SELECT a.date, SUM(counts) from (
      SELECT DAY(StartDateTime) as date, COUNT(id) counts
      FROM Table1
      WHERE DAY(StartDateTime) = DAY(EndDateTime)
      GROUP BY StartDateTime
      UNION ALL 
      SELECT DAY(EndDateTime), COUNT(id)
      FROM Table1
      WHERE DAY(StartDateTime) != DAY(EndDateTime)
      GROUP BY EndDateTime
      UNION ALL 
      SELECT DAY(StartDateTime), COUNT(id)
      FROM Table1
      WHERE DAY(StartDateTime) != DAY(EndDateTime)
      GROUP BY StartDateTime) a
GROUP BY a.date 
 

Here is SQL Fiddle link SQL Fiddle

Also replace Table1 with Jobs when running over your db context