数据库系统基础教程答案ch4 下载本文

d)

4.7.3

4.7.4

4.7.5

Males and Females subclasses are complete. Mothers and Fathers are partial. All subclasses are disjoint.

4.7.6

4.7.7

4.7.8

We convert the ternary relationship Contracts into three binary relationships between a new entity set Contracts and existing entity sets.

4.7.9 a)

b)

c)

4.7.10

A self-association ParentOf for entity set people has multiplicity 0..2 at parent role end.

In a Library database, if a patron can loan at most 12 books, them multiplicity is 0..12.

For a FullTimeStudents entity set, a relationship of multiplicity 5..* must exist with Courses (A student must take at least 5 courses to be classified FullTime.