SQL getting datediff from same field - sql

Question

I have a problem. I need to get the date difference in terms of hours in my table but the problem is it is saved in the same field. This is my table would look like.
RecNo. Employeeno recorddate recordtime recordval
1 001 8/22/2014 8:15 AM 1
2 001 8/22/2014 5:00 PM 2
3 001 8/24/2014 8:01 AM 1
4 001 8/24/2014 5:01 PM 2
1 indicates time in and 2 indicates time out. Now, How will i get the number of hours worked for each day? What i want to get is something like this.
Date hoursworked
8/22/2014 8
8/24/2014 8
I am using VS 2010 and SQL server 2005

Answer 1

You could self-join each "in" record with its corresponding "out" record and use datediff to subtract them:
SELECT time_in.employeeno AS "Employee No",
time_in.recorddate AS "Date",
DATEDIFF (hour, time_in.recordtime, time_out.recordtime)
AS "Hours Worked"
FROM (SELECT *
FROM my_table
WHERE recordval = 1) time_in
INNER JOIN (SELECT *
FROM my_table
WHERE recordval = 2) time_out
ON time_in.employeeno = time_out.employeeno AND
time_in.recorddate = time_out.recorddate

Answer 2

If you always record time in and time out for every employee, and just one per day, using a self-join should work:
SELECT
t1.Employeeno,
t1.recorddate,
t1.recordtime AS [TimeIn],
t2.recordtime AS [TimeOut],
DATEDIFF(HOUR,t1.recordtime, t2.recordtime) AS [HoursWorked]
FROM Table1 t1
INNER JOIN Table1 t2 ON
t1.Employeeno = t2.Employeeno
AND t1.recorddate = t2.recorddate
WHERE t1.recordval = 1 AND t2.recordval = 2
I included the recordtime fields as time in, time out, if you don't want them just remove them.
Note that this datediff calculation gives 9 hours, and not 8 as you suggested.
Sample SQL Fiddle

Answer 3

Using this sample data:
with table1 as (
select * from ( values
(1,'001', cast('20140822' as datetime),cast('08:15:00 am' as time),1)
,(2,'001', cast('20140822' as datetime),cast('05:00:00 pm' as time),2)
,(3,'001', cast('20140824' as datetime),cast('08:01:00 am' as time),1)
,(4,'001', cast('20140824' as datetime),cast('04:59:00 pm' as time),2)
,(5,'001', cast('20140825' as datetime),cast('10:01:00 pm' as time),1)
,(6,'001', cast('20140826' as datetime),cast('05:59:00 am' as time),2)
)data(RecNo,EmployeeNo,recordDate,recordTime,recordVal)
)
this query
SELECT
Employeeno
,convert(char(10),recorddate,120) as DateStart
,convert(char(5),cast(TimeIn as time)) as TimeIn
,convert(char(5),cast(TimeOut as time)) as TimeOut
,DATEDIFF(minute,timeIn, timeOut) / 60 AS [HoursWorked]
,DATEDIFF(minute,timeIn, timeOut) % 60 AS [MinutesWorked]
FROM (
SELECT
tIn.Employeeno,
tIn.recorddate,
dateadd(minute, datediff(minute,0,tIn.recordTime), tIn.recordDate)
as TimeIn,
( SELECT TOP 1
dateadd(minute, datediff(minute,0,tOut.recordTime), tOut.recordDate)
as TimeOut
FROM Table1 tOut
WHERE tOut.RecordVal = 2
AND tOut.EmployeeNo = tIn.EmployeeNo
AND tOut.RecNo > tIn.RecNo
ORDER BY tOut.EmployeeNo, tOut.RecNo
) as TimeOut
FROM Table1 tIn
WHERE tIn.recordval = 1
) T
yields (as desired)
Employeeno DateStart TimeIn TimeOut HoursWorked MinutesWorked
---------- ---------- ------ ------- ----------- -------------
001 2014-08-22 08:15 17:00 8 45
001 2014-08-24 08:01 16:59 8 58
001 2014-08-25 22:01 05:59 7 58
No assumptions are made about shifts not running across midnight (see case 3).
This particular implementation may not be the most performant way to construct this correlated subquery, so if there is a performance problem come back and we can look at it again. However running those tests requires a large dataset which I don't feel like constructing just now.