Question

I am making an attendance system in which I will add monthly records of employee time in and time out. At the end of the month average time in and time out will be created.

Please tell me how to apply avg() to datatype of time(7)?

declare @tblPK table
(
    timeinat varchar(13) not null,
    timeoutat varchar(13) not null
) ;

insert into @tblPK 
select cast((onattendance) as varchar(13))ONTime, 
       cast((offattendance) as varchar(13))OFFTime 
from t_attendancedetails ;

select * from @tblPK ;

This is only giving output of all entries.

Answer 1

Calculating average with a precision of millisecond using time(7) columns.

select dateadd(millisecond, avg(datediff(millisecond, onattendance, offattendance)), cast('00:00' as time(7)) )
from t_attendancedetails

The query uses datediffto get the difference in milliseconds between onattendance and offattendance. Then it uses the aggregate function avg to calculate the average difference in milliseconds and finally it uses dateadd to add the average number of milliseconds to the time(7) value 00:00.

Ref:
DATEDIFF (Transact-SQL)
DATEADD (Transact-SQL)
AVG (Transact-SQL)
CAST and CONVERT (Transact-SQL)

Update:

When calculating the average with a precision of time(7) you need to split the time in two parts because datediff and dateadd does not deal with bigint.

The time difference values is converted to nanoseconds before average is calculated and the conversion back to time(7) is done in two steps, first the seconds and then the nanoseconds.

declare @T0 time(7) = '00:00:00'
declare @G bigint = 1000000000  
declare @H bigint = 100         

select dateadd(nanosecond, cast(right(T.A, 9) as int), dateadd(second, T.A / @G, @T0))
from
  (
  select avg(
              @G * datediff(second, @T0, offattendance) + @H * right(offattendance, 7) -
              @G * datediff(second, @T0, onattendance ) + @H * right(onattendance,  7)
            )
  from t_attendancedetails
  ) as T(A)