Get total working hours from SQL table - sql

Question

I have an attendance SQL table that stores the start and end day's punch of employee. Each punch (punch in and punch out) is in a separate record.
I want to calculate the total working hour of each employee for a requested month.
I tried to make a scalar function that takes two dates and employee ID and return the calculation of the above task, but it calculate only the difference of one date between all dates.
The data is like this:
000781 2015-08-14 08:37:00 AM EMPIN 539309898
000781 2015-08-14 08:09:48 PM EMPOUT 539309886
My code is:
#FromDate NVARCHAR(10)
,#ToDate NVARCHAR(10)
,#EmpID NVARCHAR(6)
CONVERT(NVARCHAR,DATEDIFF(HOUR
,(SELECT Time from PERS_Attendance att where attt.date between convert(date,#fromDate) AND CONVERT(Date,#toDate)
AND (EmpID= #EmpID OR ISNULL(#EmpID, '') = '') AND Funckey = 'EMPIN')
,(SELECT Time from PERS_Attendance att where attt.date between convert(date,#fromDate) AND CONVERT(Date,#toDate)
AND (EmpID= #EmpID OR ISNULL(#EmpID, '') = '') AND Funckey = 'EMPOUT') ))
FROM PERS_Attendance attt

Answer 1

One more approach that I think is simple and efficient.
It doesn't require modern functions like LEAD
it works correctly if the same person goes in and out several times during the same day
it works correctly if the person stays in over the midnight or even for several days in a row
it works correctly if the period when person is "in" overlaps the start OR end date-time.
it does assume that data is correct, i.e. each "in" is matched by "out", except possibly the last one.
Here is an illustration of a time-line. Note that start time happens when a person was "in" and end time also happens when a person was still "in":
All we need to do it calculate a plain sum of time differences between each event (both in and out) and start time, then do the same for end time. If event is in, the added duration should have a positive sign, if event is out, the added duration should have a negative sign. The final result is a difference between sum for end time and sum for start time.
summing for start:
|---| +
|----------| -
|-----------------| +
|--------------------------| -
|-------------------------------| +
--|====|--------|======|------|===|=====|---|==|---|===|====|----|=====|--- time
in out in out in start out in out in end out in out
summing for end:
|---| +
|-------| -
|----------| +
|--------------| -
|------------------------| +
|-------------------------------| -
|--------------------------------------| +
|-----------------------------------------------| -
|----------------------------------------------------| +
I would recommend to calculate durations in minutes and then divide result by 60 to get hours, but it really depends on your requirements. By the way, it is a bad idea to store dates as NVARCHAR.
DECLARE #StartDate datetime = '2015-08-01 00:00:00';
DECLARE #EndDate datetime = '2015-09-01 00:00:00';
DECLARE #EmpID nvarchar(6) = NULL;
WITH
CTE_Start
AS
(
SELECT
EmpID
,SUM(DATEDIFF(minute, (CAST(att.[date] AS datetime) + att.[Time]), #StartDate)
* CASE WHEN Funckey = 'EMPIN' THEN +1 ELSE -1 END) AS SumStart
FROM
PERS_Attendance AS att
WHERE
(EmpID = #EmpID OR #EmpID IS NULL)
AND att.[date] < #StartDate
GROUP BY EmpID
)
,CTE_End
AS
(
SELECT
EmpID
,SUM(DATEDIFF(minute, (CAST(att.[date] AS datetime) + att.[Time]), #StartDate)
* CASE WHEN Funckey = 'EMPIN' THEN +1 ELSE -1 END) AS SumEnd
FROM
PERS_Attendance AS att
WHERE
(EmpID = #EmpID OR #EmpID IS NULL)
AND att.[date] < #EndDate
GROUP BY EmpID
)
SELECT
CTE_End.EmpID
,(SumEnd - ISNULL(SumStart, 0)) / 60.0 AS SumHours
FROM
CTE_End
LEFT JOIN CTE_Start ON CTE_Start.EmpID = CTE_End.EmpID
OPTION(RECOMPILE);
There is LEFT JOIN between sums for end and start times, because there can be EmpID that has no records before the start time.
OPTION(RECOMPILE) is useful when you use Dynamic Search Conditions in T‑SQL. If #EmpID is NULL, you'll get results for all people, if it is not NULL, you'll get result just for one person.
If you need just one number (a grand total) for all people, then wrap the calculation in the last SELECT into SUM(). If you always want a grand total for all people, then remove #EmpID parameter altogether.
It would be a good idea to have an index on (EmpID,date).

Answer 2

My approach would be as follows:
CREATE FUNCTION [dbo].[MonthlyHoursByEmpID]
(
#StartDate Date,
#EndDate Date,
#Employee NVARCHAR(6)
)
RETURNS FLOAT
AS
BEGIN
DECLARE #TotalHours FLOAT
DECLARE #In TABLE ([Date] Date, [Time] Time)
DECLARE #Out TABLE ([Date] Date, [Time] Time)
INSERT INTO #In([Date], [Time])
SELECT [Date], [Time]
FROM PERS_Attendance
WHERE [EmpID] = #Employee AND [Funckey] = 'EMPIN' AND ([Date] > #StartDate AND [Date] < #EndDate)
INSERT INTO #Out([Date], [Time])
SELECT [Date], [Time]
FROM PERS_Attendance
WHERE [EmpID] = #Employee AND [Funckey] = 'EMPOUT' AND ([Date] > #StartDate AND [Date] < #EndDate)
SET #TotalHours = (SELECT SUM(CONVERT([float],datediff(minute,I.[Time], O.[Time]))/(60))
FROM #in I
INNER JOIN #Out O
ON I.[Date] = O.[Date])
RETURN #TotalHours
END

Answer 3

Assuming the entries are properly paired (in -> out -> in -> out -> in etc).
SQL Server 2012 and later:
DECLARE #Year int = 2015
DECLARE #Month int = 8
;WITH
cte AS (
SELECT EmpID,
InDate = LAG([Date], 1) OVER (PARTITION BY EmpID ORDER BY [Date]),
OutDate = [Date],
HoursWorked = DATEDIFF(hour, LAG([Date], 1) OVER (PARTITION BY EmpID ORDER BY [Date]), [Date]),
Funckey
FROM PERS_Attendance
)
SELECT EmpID,
TotalHours = SUM(HoursWorked)
FROM cte
WHERE Funckey = 'EMPOUT'
AND YEAR(InDate) = #Year
AND MONTH(InDate) = #Month
GROUP BY EmpID
SQL Server 2005 and later:
;WITH
cte1 AS (
SELECT *,
rn = ROW_NUMBER() OVER (PARTITION BY EmpID ORDER BY [Date])
FROM PERS_Attendance
),
cte2 AS (
SELECT a.EmpID, b.[Date] As InDate, a.[Date] AS OutDate,
HoursWorked = DATEDIFF(hour, b.[Date], a.[Date])
FROM cte1 a
LEFT JOIN cte1 b ON a.EmpID = b.EmpID and a.rn = b.rn + 1
WHERE a.Funckey = 'EMPOUT'
)
SELECT EmpID,
TotalHours = SUM(HoursWorked)
FROM cte2
WHERE YEAR(InDate) = #Year
AND MONTH(InDate) = #Month
GROUP BY EmpID