About primary keys

Every feature on a map has a unique "primary key" that can be used to link CSV or plain-text data to features on an existing map. Primary keys are usually an alphanumeric string, such as a postal code, a Federal Information Processing Standard (FIPS) code, or an ISO-3166 code.

If two imported features have the same primary key, they will be regarded as a single feature. It is not possible to change a feature's primary key after import.

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