1、SolutionsChapter 4 4.1.14.1.2a)b)c)In c we assume that a phone and address can only belong to a single customer (1-m relationship represented by arrow into customer). d)In d we assume that an address can only belong to one customer and a phone can exist at only one address.If the multiplicity of abo
2、ve relationships were m-to-n, the entity set becomes weak and the key ssNo of customers will be needed as part of the composite key of the entity set.In c&d, we convert attributes phones and addresses to entity sets. Since entity sets often become relations in relational design,we must consider more
3、 efficient alternatives. Instead of querying multiple tables where key values are duplicated, we can also modify attributes: (i) Phones attribute can be converted into HomePhone, OfficePhone and CellPhone. (ii) A multivalued attribute such as alias can be kept as an attribute where a single column c
4、an be used in relational design i.e. concatenate all values. SQL allows a query “like %Junius%“ to search the multiple values in a column alias.4.1.3 4.1.4 a)b)c)The relationship “played“ between Teams and Players is similar to relationship “plays“ between Teams and Players. 4.1.5 4.1.6 The informat
5、ion about children can be ascertained from motherOf and fatherOf relationships. Attribute ssNo is required since names are not unique.4.1.74.1.8a)(b)4.1.9AssumptionsA Professor only works in at most one department.A course has at most one TA.A course is only taught by one professor and offered by one department.Students and professors have been assigned unique email ids.A course is uniquely identified by the course no, section no, and semester (e.g. cs157-3 spring 09).4.1.10
