I'm learning for a test at school from database systems, and I'havent found similar example on the Internet and I'm not sure. What is the cardinality of following relationship ?
I would say 1:1. Some of my friends say that 1:M. Am I right?
I've been thinking as follows: ET1 is tightly coupled with ET2 using atr3(FK) but also has its own atr1(PK). So ET2:ET1 is 1:M. But then there ist atr1(FK) in ET2 and this relationship sounds to me like that ET2 that has ET1s can be exactly linked only to one of its ET1 so the resulting relationship should be 1:1.
What do you think ?
Thank you very much guys.