Which of the following is NOT a good primary key?

مندرجہ ذیل میں سے کون اچھی پرائمری کلید نہیں ہے؟

Student ID number

Zip code

Serial security number

Order number

A primary key must be unique for each record and never change.

Zip code is not unique (many people can share the same zip code), so it's not suitable as a primary key.