I am facing the following problem:
I have a table with customer information like the customer number, i.e.
customerID set up as the primary key, and, besides a number of other data, also a country value in the form of a country code,
However, customer data from other countries should also be imported into this table. Although the customer numbers are unique within a country, they are not cross-country. Customer numbers should not be changed for organizational reasons.
How can a key still be ensured for each customer in this table?