[請益]Relational model
各位大大好
小弟在學習database processing (David M.Kroenke)
一些課後作業有些不了解的地方 請各位大大解惑 謝謝
題目是這樣的
SHIPMENT (ShipmentNumber, VendorName, VendorContact, VendorFax, DepartureDate,
ArrivalDate, CountryOfOrigin, Destination, ShipmentCost, InsuranceValue,
Insurer)
(因為沒有給實際的table 所以無法確切知道各column之間的關係)
1.Write a funcitional dependency that express the fact that
the cost of a shipment between two cities is always the same.
這題小弟應該沒想錯 (CountryOfOrigin, Destination)->ShipmentCost
之後就很不能理解了
2.Write a fun~ dependency that express ~
the insurance value is always the same for a given vendor
3.~
the insurance value is always the same for a given vendor and Country of Origin
小弟的想法是這樣
ShipmentNumber->(VendorName,DepartureDate,ArrivalDate,Destination, Insurer)
VendorName->(VendorContact, VendorFax,CountryOfOrigin)
(CountryOfOrigin,Destination)->ShipmentCost
(ShipmentCost,Insurer)->InsuranceValue
請問各位 小弟這樣有沒有錯誤
如果沒有問題的話 要往哪方面才能找出2 3 的答案呢 ?
謝謝
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