Hi Syakirah,

I think you can do this by few methods, let me specify one method.

You can use one aggregate to fetch the all the booking first then you can use a calculated attribute in that aggregate to check whether the start date time entered by using the expression such as "BookingDetail.Startdatetime <= InputBookingDetail.StartDateTime and InputBookingDetail.StartDateTime <= BookingDetail.EndDateTime", this will give you true as output if the condition matches and you can repeat the same for the end date time.

After that you can use List Any server action to check any of the record in the aggregate is true in either of the 2 calculated attributes.

This can help you to avoid the duplicate entries, I think so. 

@Syakirah

To achieve this you need to add a filter condition in the existing booking entity aggregate - 

DB_Date = InputParam_BookingDate and
((DB_StartTime <= InputParam_ endTime and DB_ EndTime >= InputParam_ startTime) or (DB_ StartTime < InputParam_ endTime and DB_ EndTime > InputParam_ startTime))

after that -check if the above aggregate  Isempty?
if Yes - allow to save 
if No - Do not allow for booking

This should work in your scenario

Cheers,
Shriyash Dixit

Hi @Syakirah ,
In Booking_Detail Aggregate filter by Room no , Booking date get from the inputs and also filter by
start time is greater than End time . After check the condition if Aggregate is empty you allow to create the record.
Thanks