For short haul flights:
SAS has three main hubs, CPH, ARN and OSL (In that order). The crew belongs to one of these stations. So CPH crew operates all flights to and from Denmark. Flights to, from and within Sweden are operated by ARN crew, flights to, from and within Norway are operated by OSL crew. On flights between the three countries you will find that all three stations can operate the flight (e.g. OSL-CPH is operated by planes from CPH and OSL, but not ARN).

There is a requirement to speak one of the Scandinavian languages to get hired by SAS. So to get hired at CPH you need to know Danish, Swedish or Norwegian. So if you have a Swedes Purser on a flight from CPH, you can be sure that she is hired in Denmark.

For intercontinental flights:
There is (at least used to be) an agreement between SAS and the unions that all three nationalities are to be represented on all Intercontinental flights to and from CPH. So you will always find the three Scandinavian nationalities represented on IC flights from CPH. The same agreement do not apply for IC flights from OSL and ARN, thus the IC traffic from there is limited