SQL Door access - sql

Question

I'm pretty new to sql and have been set a task of creating a query which will give me the first and last entrance of each user and how long they were in the office for.
So far i have got the below
SELECT
CONVERT(VARCHAR(10),evts.Eventtime,101) as Date,
CONVERT(VARCHAR(10),evts.Eventtime,108) as Time,
un.UserName AS [User],
case
when p.Name = 'ACU:4321104 - 5th floor (In)' then '5th entrance'
when p.name = 'ACU:4321176 - 4th floor (In)' then '4th entrance'
when p.name = 'ACU:4321176 - 4th floor (Out)' then '4th exit'
when p.name = 'ACU:4321104 - 5th floor (Out)' then '5th exit'
when p.name = 'ACU:4321158 - 3rd Floor (In)' then '3rd entrance'
when p.name = 'ACU:4321158 - 3rd Floor (Out)' then '3rd exit'
end as [where]
FROM
Net2Events.dbo.Events AS evts LEFT OUTER JOIN
dbo.vw_UserNamesFS AS un ON evts.UserID = un.UserID LEFT OUTER JOIN
Net2Events.dbo.[Event subtype description] AS esd ON evts.EventSubType = esd.EventSubType LEFT OUTER JOIN
Net2Events.dbo.[Event description] AS ed ON evts.EventType = ed.EventType LEFT OUTER JOIN
dbo.Peripherals AS p ON evts.Address = p.Address AND evts.SubAddr = p.SubAddr
WHERE evts.EventTime >= dateadd(day,datediff(day,1,GETDATE()),0)
AND evts.EventTime < dateadd(day,datediff(day,0,GETDATE()),0)
Which gives access to every entrance and exit. Any help would be highly appreciated.
Thanks

Answer 1

You will almost certainly need to adjust your where clause if this is more than a one off report, but for all EventTimes between those two dates, this query will give you the first and last EventTime by each user and the time between those in minutes.
If you need to further break this down by specific flors, you can add your where field back in (Though I would recommend against that name, as it is a SQL keyword) to both the select and the group by:
SELECT un.UserName AS [User]
,MIN(evts.Eventtime) as FirstEvent
,MAX(evts.Eventtime) as LastEvent
,DATEDIFF(minute,MIN(evts.Eventtime),MAX(evts.Eventtime)) as TimeDifference
FROM Net2Events.dbo.Events AS evts
LEFT OUTER JOIN dbo.vw_UserNamesFS AS un
ON evts.UserID = un.UserID
LEFT OUTER JOIN Net2Events.dbo.[Event subtype description] AS esd
ON evts.EventSubType = esd.EventSubType
LEFT OUTER JOIN Net2Events.dbo.[Event description] AS ed
ON evts.EventType = ed.EventType
LEFT OUTER JOIN dbo.Peripherals AS p
ON evts.Address = p.Address
AND evts.SubAddr = p.SubAddr
WHERE evts.EventTime >= dateadd(day,datediff(day,1,GETDATE()),0)
AND evts.EventTime < dateadd(day,datediff(day,0,GETDATE()),0)
GROUP BY un.UserName
I think you will need to do more than just the first and last event however, as I don't think there is a production database in the world with 100% correct data. This means you will need to find the earliest In event and the latest Out event and then check that these make sense.
You can 'exclude' certain rows from aggregates like min and max with a case statement that substitutes an impossible value way beyond the normal range which you can handle if needs be later on:
min(case when <criteria to include> then EventTime else '29990101' end)
Edit to add in response to comment
To format your Time Difference into various date elements, you need to start with your largest date part - ie: Days? Hours? - and then work down from there. Start with working out how many full days you have, which for a value in minutes means doing integer division by 60 to get the number of full hours and then by 24 to get the number of full days:
#difference / 60 / 24
We then need the number of full hours, minus all the hours taken up in the full days. To do this we can do the above calculation by use modulo instead of division to find the remainder of the hours that don't create a full day:
#difference / 60 % 24
And then to find the number of minutes left over, we simply need to find the remainder of a division by 60:
#difference % 60
Do some cast/converting to get the right formatting and you have your difference in Days, Hours and Minutes:
declare #start datetime = getdate() - 400.255;
declare #end datetime = getdate();
declare #difference int = datediff(minute,#start,#end);
select cast(#difference/60/24 as nvarchar(5)) + case when #difference/60/24 = 1 then ' Day, ' else ' Days, ' end
+ cast(#difference/60%24 as nvarchar(5)) + case when #difference/60%24 = 1 then ' Hour, ' else ' Hours, ' end
+ cast(#difference%60 as nvarchar(5)) + case when #difference%60 = 1 then ' Minute' else ' Minutes' end;
which returns: 400 Days, 6 Hours, 7 Minutes
Of course, if you only ever want Hours and Minutes in hh:mm format and are super confident this time difference will never go over 23 hours, 59 minutes and 59.9999999 seconds, you can simply convert the difference to a time value by adding it to an arbitrary date, and formatting accordingly in your front end application:
cast(dateadd(minute,#difference,0) as time)
Which returns: 06:07:00.0000000 for the parameters above - Note the missing 400 days.