What is the key for this relation?

farfrom
15 pts.
Tags:
ERD
ERD (Entity Relationship Diagram)
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
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  • CharlieBrowne
    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.
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  • farfrom
    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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