In Coredata, how to get all IDs for specific table?

I want to fetch all IDs from a coredata table. For example, There is a Table called Person. There is a personId to uniquely identify a record. I want to fetch all personId stayed in Person table. I don't know how I can do a query for that.

In SQLite Manager, I could have do it by executing the following query:

SELECT ZPERSONID FROM ZPERSON;

But I have no idea how I can do it for iOS Coredata.

Thanks in Advance !!!