I want to get the calendar data every day that was created or updated at yesterday.

I get events on the specified calendar with google-calendar-api at [here](https://developers.google.com/calendar/v3/reference/events/list?authuser=1).

For example,today,I want to get the events of calendar data was created or updated at yesterday.

If I can find the primary key of this method, then I update the data with the primary key to the database. If can't find the primary key in database with primary key in response, represents new data is exists,so I insert the new data into the database. If the `status` of the data is `cancelled`, then I delete the data from the database. 

Now I have the administrator's account. I can get the gmail account of all employees in my company, and I have added these accounts to my calendar.I can get employees'calendarId, but I want to know which fields I should use as the primary key to do this, use `calendarId` and `iCalUID` to get different data or only use `iCalUID` to get different data?

What is the primary key of the method Events:list?