Is a custom object dedupe field required?

[Kim_Gandy1]

I'm building a custom object for conference attendance. My link field is "email address," but I want each year the person attended the conference to be a new entry to the object. To my understanding, the dedupe field would override the value in an existing conference entry. 

Is a custom object dedupe field required?

[SanfordWhiteman]

You wouldn't use a dedupe field that would violate the one-to-many relationship.

[Kim_Gandy1 · Accepted solution]

At least one dedupe field is required, and cannot be datetime field. 

[SanfordWhiteman]

Note that if the intent is to dedupe on a timestamp, like for timeseries data, you don't need an DateTime field. A microsecond timestamp (or even a nanosecond timestamp) can be stored in an Integer.