如何找到两个日期范围之间的总时差

Question

I have created a procedure which returns time difference in minutes between 2 time ie ShiftStartTime, ShiftEndtime.

Now problem is that if i pass 2 date ranges then how i will calculate total shiftTime between those 2 dates eg TimeDifference returns me 480 min for today but i want to find total ShiftDifference for 3 days or more, then how i will add TimeDifference for more than 1 day ?

CREATE PROCEDURE GetShiftTotalDuration

 @ShiftID int = 9,
 @FromDate DateTime,
 @ToDate DateTime

AS
BEGIN

    Declare @TimeDifference int
    Declare @ShiftStartTime time
    Declare @ShiftEndTime time

    Set @ShiftStartTime = (Select DeparmentShiftsHistory.StartTime from DeparmentShiftsHistory 
                           where DeparmentShiftsHistory.Shift_ID= 9)
    Set @ShiftEndTime = (Select DeparmentShiftsHistory.EndTime from DeparmentShiftsHistory
                           where DeparmentShiftsHistory.Shift_ID= 9)
    Set @TimeDifference = (Select DATEDIFF(mi,@ShiftStartTime,@ShiftEndTime)) --Returns time difference in seconds



END
GO

Answer 1

I will calculate total shiftTime between those 2 dates

You mention that you will calculate difference between two dates but in your code you declare the variables as time

Declare @ShiftStartTime time
Declare @ShiftEndTime time

Thus DATEDIFF(mi,@ShiftStartTime,@ShiftEndTime) only the difference between the times not the dates

If you want to get the difference between dates you need use datetime datatype

On a side note, you have declared input parameters which have not been used in the proocedure as mentioned by Pradeep