Count number of days each employee take vacation in a month SQL Server - sql

Question

I have this table:
Vacationtbl:
ID Start End
-------------------------
01 04/10/17 04/12/17
01 04/27/17 05/02/17
02 04/13/17 04/15/17
02 04/17/17 04/20/17
03 06/14/17 06/22/17
Employeetbl:
ID Fname Lname
------------------
01 John AAA
02 Jeny BBB
03 Jeby CCC
I like to count the number of days each employee take vacation in April.
My query:
SELECT
SUM(DATEDIFF(DAY, Start, End) + 1) AS Days
FROM
Vacationtbl
GROUP BY
ID
01 returns 9 (not correct)
02 returns 7 (correct)
How do I fix the query so that it counts until the end of month and stops at end of month. For example, April has 30 days. On second row, Employee 01 should counts 4/27/17 until 4/30/17. And 05/02/17 is for May.
Thanks

Answer 1

The Tally/Calendar table is the way to go. However, you can use an ad-hoc tally table.
Example
Select Year = Year(D)
,Month = Month(D)
,ID
,Days = count(*)
From Vacationtbl A
Cross Apply (
Select Top (DateDiff(DAY,[Start],[End])+1) D=DateAdd(DAY,-1+Row_Number() Over (Order By (Select Null)),[Start])
From master..spt_values
) B
-- YOUR OPTIONAL WHERE STATEMENT HERE --
Group By ID,Year(D),Month(D)
Order By 1,2,3
Returns
Year Month ID Days
2017 4 01 7
2017 4 02 7
2017 5 01 2
EDIT - To Show All ID even if Zero Days
Select ID
,Year = Year(D)
,Month = Month(D)
,Days = sum(case when D between [Start] and [End] then 1 else 0 end)
From (
Select Top (DateDiff(DAY,'05/01/2017','05/31/2017')+1) D=DateAdd(DAY,-1+Row_Number() Over (Order By (Select Null)),'05/01/2017')
From master..spt_values
) D
Cross Join Vacationtbl B
Group By ID,Year(D),Month(D)
Order By 1,2,3
Returns
ID Year Month Days
1 2017 5 2
2 2017 5 0
dbFiddle if it Helps
EDIT - 2 Corrects for Overlaps (Gaps and Islands)
--Create Some Sample Data
----------------------------------------------------------------------
Declare #Vacationtbl Table ([ID] varchar(50),[Start] date,[End] date)
Insert Into #Vacationtbl Values
(01,'04/10/17','04/12/17')
,(01,'04/27/17','05/02/17')
,(02,'04/13/17','04/15/17')
,(02,'04/17/17','04/20/17')
,(02,'04/16/17','04/17/17') -- << Overlap
,(03,'05/16/17','05/17/17')
-- The Actual Query
----------------------------------------------------------------------
Select ID
,Year = Year(D)
,Month = Month(D)
,Days = sum(case when D between [Start] and [End] then 1 else 0 end)
From (Select Top (DateDiff(DAY,'04/01/2017','04/30/2017')+1) D=DateAdd(DAY,-1+Row_Number() Over (Order By (Select Null)),'04/01/2017') From master..spt_values ) D
Cross Join (
Select ID,[Start] = min(D),[End] = max(D)
From (
Select E.*,Grp = Dense_Rank() over (Order By D) - Row_Number() over (Partition By ID Order By D)
From (
Select Distinct A.ID,D
From #Vacationtbl A
Cross Apply (Select Top (DateDiff(DAY,A.[Start],A.[End])+1) D=DateAdd(DAY,-1+Row_Number() Over (Order By (Select Null)),A.[Start]) From master..spt_values ) B
) E
) G
Group By ID,Grp
) B
Group By ID,Year(D),Month(D)
Order By 1,2,3
Returns
ID Year Month Days
1 2017 4 7
2 2017 4 8
3 2017 4 0

Answer 2

Without a dates table, you could use
select Id
,sum(case when [end]>'20170430' and [start]<'20170401' then datediff(day,'20170401','20170430')+1
when [end]>'20170430' then datediff(day,[start],'20170430')+1
when [start]<'20170401' then datediff(day,'20170401',[end])+1
else datediff(day,[start],[end])+1
end) as VacationDays
from Vacationtbl
where [start] <= '20170430' and [end] >= '20170401'
group by Id
There are 3 conditions here
Start is before this month and the end is after this month. In this case you subtract the end and start dates of the month.
End is after month end and start is in the month, in this case subtract month end date from the start.
Start is before this month but the end is in the month. In this case subtract month start date and the end date.
Edit: Based on the OP's comments that the future dates have to be included,
/*This recursive cte generates the month start and end dates with in a given time frame
For Eg: all the month start and end dates for 2017
Change the start and end period as needed*/
with dates (month_start_date,month_end_date) as
(select cast('2017-01-01' as date),cast(eomonth('2017-01-01') as date)
union all
select dateadd(month,1,month_start_date),eomonth(dateadd(month,1,month_start_date)) from dates
where month_start_date < '2017-12-01'
)
--End recursive cte
--Query logic is the same as above
select v.Id
,year(d.month_start_date) as yr,month(d.month_start_date) as mth
,sum(case when v.[end]>d.month_end_date and v.[start]<d.month_start_date then datediff(day,d.month_start_date,d.month_end_date)+1
when v.[end]>d.month_end_date then datediff(day,v.[start],d.month_end_date)+1
when v.[start]<d.month_start_date then datediff(day,d.month_start_date,v.[end])+1
else datediff(day,v.[start],v.[end])+1
end) as VacationDays
from dates d
join Vacationtbl v on v.[start] <= d.month_end_date and v.[end] >= d.month_start_date
group by v.id,year(d.month_start_date),month(d.month_start_date)

Answer 3

Assuming you want only one month and you want to count all days, you can do this with arithmetic. A separate calendar table is not necessary. The advantage is performance.
I think this would be easier if SQL Server supported least() and greatest(), but case will do:
select id,
sum(1 + datediff(day, news, newe)) as vacation_days_april
from vactiontbl v cross apply
(values (case when [start] < '2017-04-01' then cast('2017-04-01' as date) else [start] end),
(case when [end] >= '2017-05-01' then cast('2017-04-30' as date) else [end] end)
) v(news, newe)
where news <= newe
group by id;
You can readily extend this to any month:
with m as (
select cast('2017-04-01' as date) as month_start,
cast('2017-04-30' as date) as month_end
)
select id,
sum(1 + datediff(day, news, newe)) as vacation_days_aprile
from m cross join
vactiontbl v cross apply
(values (case when [start] < m.month_start then m.month_start else [start] end),
(case when [end] >= m.month_end then m.month_end else [end] end)
) v(news, newe)
where news <= newe
group by id;
You can even use a similar idea to extend to multiple months, with a different row for each user and each month.

Answer 4

You can use a Calendar or dates table for this sort of thing.
For only 152kb in memory, you can have 30 years of dates in a table with this:
/* dates table */
declare #fromdate date = '20000101';
declare #years int = 30;
/* 30 years, 19 used data pages ~152kb in memory, ~264kb on disk */
;with n as (select n from (values(0),(1),(2),(3),(4),(5),(6),(7),(8),(9)) t(n))
select top (datediff(day, #fromdate,dateadd(year,#years,#fromdate)))
[Date]=convert(date,dateadd(day,row_number() over(order by (select 1))-1,#fromdate))
into dbo.Dates
from n as deka cross join n as hecto cross join n as kilo
cross join n as tenK cross join n as hundredK
order by [Date];
create unique clustered index ix_dbo_Dates_date
on dbo.Dates([Date]);
Without taking the actual step of creating a table, you can use it inside a common table expression with just this:
declare #fromdate date = '20170401';
declare #thrudate date = '20170430';
;with n as (select n from (values(0),(1),(2),(3),(4),(5),(6),(7),(8),(9)) t(n))
, dates as (
select top (datediff(day, #fromdate, #thrudate)+1)
[Date]=convert(date,dateadd(day,row_number() over(order by (select 1))-1,#fromdate))
from n as deka cross join n as hecto cross join n as kilo
cross join n as tenK cross join n as hundredK
order by [Date]
)
select [Date]
from dates;
Use either like so:
select
v.Id
, count(*) as VacationDays
from Vacationtbl v
inner join Dates d
on d.Date >= v.[Start]
and d.Date <= v.[End]
where d.Date >= '20170401'
and d.Date <= '20170430'
group by v.Id
rextester demo (table): http://rextester.com/PLW73242
rextester demo (cte): http://rextester.com/BCY62752
returns:
+----+--------------+
| Id | VacationDays |
+----+--------------+
| 01 | 7 |
| 02 | 7 |
+----+--------------+
Number and Calendar table reference:
Generate a set or sequence without loops - 2 - Aaron Bertrand
The "Numbers" or "Tally" Table: What it is and how it replaces a loop - Jeff Moden
Creating a Date Table/Dimension in sql Server 2008 - David Stein
Calendar Tables - Why You Need One - David Stein
Creating a date dimension or calendar table in sql Server - Aaron Bertrand

Answer 5

Try this,
declare #Vacationtbl table(ID int,Startdate date,Enddate date)
insert into #Vacationtbl VALUES
(1 ,'04/10/17','04/12/17')
,(1 ,'04/27/17','05/02/17')
,(2 ,'04/13/17','04/15/17')
,(2 ,'04/17/17','04/20/17')
-- somehow convert your input into first day of month
Declare #firstDayofGivenMonth date='2017-04-01'
Declare #LasttDayofGivenMonth date=dateadd(day,-1,dateadd(month,datediff(month,0,#firstDayofGivenMonth)+1,0))
;with CTE as
(
select *
,case when Startdate<#firstDayofGivenMonth then #firstDayofGivenMonth else Startdate end NewStDT
,case when Enddate>#LasttDayofGivenMonth then #LasttDayofGivenMonth else Enddate end NewEDT
from #Vacationtbl
)
SELECT
SUM(DATEDIFF(DAY, NewStDT, NewEDT) + 1) AS Days
FROM
CTE
GROUP BY
ID