MS Access \\ Jet SQL-员工上班和下班时间，同一张表，每个员工的总工作时间

Question

I have the below table named 'timings'. It holds the comings and goings of staff members (morn_in, morn_out, afternoon_in, afternoon_out).

timings table What I would like to achieve is an output grouped by staff_ref, SUM of their hours worked, like so;

staff_ref|   total_worked|   
   U1            18:00

I currently use 4 separate queries to select each of the 'type' (morn_in, morn_out etc), the one for type='morn_in' is below, this query is called [101 am in] (it gets referenced later);

SELECT 
staff_ref
, time
, Format([date],"dd/mm/yyyy") AS t_date
FROM timings
WHERE (((type)='morn_in'));  

I then SUM the DateDiff between the morning times;

SELECT 
[101 am in].staff_ref
, Sum(DateDiff("n",[101 am in].[time],[102 am out].[time])) AS morning_mins

FROM [101 am in] INNER JOIN [102 am out] 
 ON ([101 am in].staff_ref = [102 am out].staff_ref) 
 AND ([101 am in].date = [102 am out].date)
GROUP BY [101 am in].staff_ref;

And then SUM the datediff on the afternoon times (the same as above) separately in another query, then I add the result of those two queries together to get my total.

As you can see its very convoluted, and its not simple to explain.

I would like to know how I can combine the queries so I only need one statement to return the results if possible.

If I've explained it terribly then let me know and I'll make amendments.
Thanks

Edit 1 - 03/07/2018
I have used the code below to pull the data I need, since its a 'time' data type I had to calculate the total minutes then perform \\60 for the hours and MOD 60 for the minutes as the results were over 24 hours.

SELECT 
staff_ref, 
CLng(24*60*CDate(Sum(IIf([type]='morn_out',[time],0)-IIf([type]='morn_in',[time],0)+
IIf([type]='afternoon_out',[time],0)-IIf([type]='afternoon_in',[time],0)))) AS time_mins,
[time_mins]\60 & Format([time_mins] Mod 60,"\:00") AS convert_backHHMM

FROM timings

GROUP BY 
staff_ref, 
fix(time)
;

I would like to know how I would handle the possibility of the table having a "morning_out" time but NO "morning_in" time (or vice versa). [The front end of the system does protect against this, but I'm really curious and want to learn}.

Thanks for any assistance

Answer 1

Try this:

SELECT 
    staff_ref,
    Sum(IIf([Type] = "morn_out", [date], 0) - IIf([Type] = "morn_in", [date], 0) +
        IIf([Type] = "afternoon_out", [date], 0) - IIf([Type] = "afternoon_in", [date], 0)) As TotalTime
FROM 
    [101 am in]
GROUP BY
    staff_ref,
    Fix([date]);

Apply a format to TotalTime of, say, h:nn