我有一个问题,他们要求我获得函数依赖关系,但我不完全确定如果我正确地得到它们,这个主题似乎有点混乱,我想知道你们是否可以复查对我来说还是纠正我,如果我错了,请!需要帮助搞清函数依赖关系
Company(companyID, companyName, cityName, country, assets)
Department(deptID, deptName, companyID, cityName, country, deptMgrID)
City(cityID, cityName, country)
-Two different companies cannot have the same company ID
-Two different departments cannot have the same deptID
-Two different cities cannot have the same cityID
-Two different cities in the same country cannot have the same name.
-The company name and the city it’s located in determine the company ID.
-Two departments in the same company must have different names.
-One manager cannot run two different departments.
这些都是文件描述符,我想出了:
companyID -> companyName,cityName,country,assets
deptID -> deptName,companyID,cityName,country,deptMgrID
cityID -> cityName,country
country,cityID -> cityName
companyName,cityName -> companyID
deptID -> deptMgrID
deptID,country -> deptName