calculating working hours in a month - sql

Question

I am working on an attendance software in asp.net, in it i have to make a report which will tell the user about the hours and everything...so far i have created the basic functionality of the system, i.e. the user can check in and check out...i am stuck at making the report...
I have to calculate the working hours for every month, so the user can compare his hours with the total hours...what i had in mind was to create a stored procedure which when given a month name and a year, returns an int containing working hours for that month....but i can seem to get at it....
so far i found out how to create a date from a given month and a date, and found out the last day of that month, using which i can find out the total days in month...now i cant seem to figure out how do i know how much days to subtract for getting the working days.
here's the so far code..
declare
#y int,
#m int,
#d int,
#date datetime
set #y = 2012
set #m = 01
set #d = 01
----To create the date first
select #date = dateadd(mm,(#y-1900)* 12 + #m - 1,0) + (#d-1)
----Last Day of that date
SELECT DATEADD(s,-1,DATEADD(mm, DATEDIFF(m,0,#date)+1,0))
any help will be appreciated guys, thanks in advance....

Answer 1

The #theDate is any date on the month you want to calculate the work days. This approach does not take care about holidays.
DECLARE #theDate DATETIME = GETDATE()
SELECT MONTH(#theDate) [Month], 20 + COUNT(*) WorkDays
FROM (
SELECT DATEADD(MONTH, DATEDIFF(MONTH, 0, #theDate), 28) AS theDate
UNION
SELECT DATEADD(MONTH, DATEDIFF(MONTH, 0, #theDate), 29)
UNION
SELECT DATEADD(MONTH, DATEDIFF(MONTH, 0, #theDate), 30)
) AS d
WHERE DATEPART(DAY, theDate) > 28
AND DATEDIFF(DAY, 0, theDate) % 7 < 5

Answer 2

Here you can consider the below sql server code to get the first and
last day of the given month and also ignore all the Saturdays and Sundays.
DECLARE #curr_date datetime=getdate()
DECLARE #st_date datetime,#ed_date datetime
select #st_date=DATEADD(mm,datediff(mm,0,#curr_date),0),#ed_date = DATEADD(mm,datediff(mm,-1,#curr_date),-1)
--select #st_date as first_day,#ed_date as last_day
SET DATEFIRST 1 --Monday as first day of week
select DATEADD(dd,number,#st_date) from master..spt_values
where DATEDIFF(dd,DATEADD(dd,number,#st_date),#ed_date) >= 0 and type='P'
and DATEPART(DW,DATEADD(dd,number,#st_date)) <> 6
and DATEPART(DW,DATEADD(dd,number,#st_date)) <> 7
But inorder to calculate the actual working hours, you will have to take into the consideration of following thigs
1.Calculate the time interval between swipe-in and swipe-outs between start and end time for a day.
2.Exclude all the time gap(employee not in office)
3.Consider the company holidays.
etc

Answer 3

Here is a UDF to count work days. You can pass any date of a month to this function. But usually you should use actual "calendar" table to calculate work days and insert in this table weekends, holidays,... and so on.
CREATE FUNCTION dbo.WorkDaysCount (#Date datetime)
RETURNS int AS
BEGIN
DECLARE #BeginOfMonth datetime
SET #BeginOfMonth=DATEADD(DAY,-DAY(#Date)+1,#Date);
DECLARE #EndOfMonth datetime
SET #EndOfMonth=DATEADD(Day,-1,DATEADD(Month,1,#BeginOfMonth));
DECLARE #cDate datetime
set #cDate=#BeginOfMonth
Declare #WorkDaysCount int
SET #WorkDaysCount=0
while #cDate<=#EndOfMonth
begin
if DATEPART(dw,#cDate) not in (1,7) SET #WorkDaysCount=#WorkDaysCount+1 -- not a Sunday or Saturday change (1,7) to (6,7) if you have other week start day (Monday).
set #cDate=#cDate+1;
end;
return (#WorkDaysCount);
END