发布时间 : 星期一 文章数据库系统基础教程答案ch4更新完毕开始阅读
b)
c)
Again from Augmentation rule of Functional Dependency, given BM -> D then
BMN -> D
Thus we can just add an arrow entering Doctors to fig 4.15. Below figure represents more accurate information however.
4.2.6 a)
b) Transitivity and Augmentation rules of Functional Dependency allow arrow entering Mothers from Births. However, a new relationship in below figure represents more accurate information.
c)
Design flaws in abc above 1. As suggested above, using Transitivity and
Augmentation rules of Functional Dependency, much simpler design is possible.
4.2.7
In below figure there exists a many-to-one relationship between Babies and Births and another many-to-one relationship between Births and Mothers. From transitivity of relationships, there is a many-to-one relationship between Babies and Mothers. Hence a baby has a unique mother while a birth can allow more than one baby.
4.3.1 a)