Find Duplicate entries and label as duplicate

[NyeinChan]

Dear Community,

I'm trying to make an appointment module. In the beginning, no problem happened but when some people use the app at the same time and make appointments at the same slot, duplicate entries occur.

I'd like to know a way to check duplicate times in the specific column.

In the following table, I want to check the values in the time_id. Each row has unique values. If more than one occurrence is found, I want to label as a duplicate in another column. 

I'll use that duplicate column to build a new view or group . This will allow users to easily identify duplicate bookings and assign a new one accordingly.

Is there any formula or method to do this process? 

Thank you.

NyeinChan

[Marc_Dillon]

Search for "prevent duplicates" to see the general expressions used to determine duplicates, and modify them as needed for your situation.