Please look at the ERD http://www.mepopo.com/image/1/38504
If I mapping the ERD into relational database schema R(k1, k2, k3, a, b)
(which is before normalization).
What will be the key for R?
Thanks a lot!
Jean
This seems to be a homework question and we do not do homework. How about you give us your answer and explain your reasoning for your choice. We may help you out then.
Hi Charlie,
Thanks for your reply. Since I am learning Database from some book, and there is a passage about how to mapping ERD to relational schema, about N-ary relationship too few examples for me to clear the concept, I search from web to find this question.
According my learning, the key is k3, because the cardinality constraints for the other two participating entity types E1, E2 are both "1" , only the cardinality constraints on E3 is "N". This is my answer, is it right?
and also , is this means any relationship instance in E3 uniquely determines the instance of E1,E2 combination ?
Thanks in advance
Jean
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