In the context of this exercise, given a value that is not a unique identifier, can we determine a unique identifier?
A non-unique identifier value would be any column other than
No, if you are given a value other than a unique identifier column, like
customer_id, we cannot determine a unique identifier for the value.
What this means is, say we’re given a customer name of “John Smith”. There is no guarantee that there is only one “John Smith” within the
customers table. There could one, or even a dozen entries with this name.
customer_id, we can always determine their
customer_name. But, the other way would not apply, because if we were given a
customer_name, we could not determine their
customer_id. Given the name “John Smith”, there might be 10
customer_id's with that name.
As a result, it is either very difficult and usually not possible to determine
id values given a non-unique column value, which are columns other than the