5.19 Give examples of binary 1:N relationships, other than those in this text, for (a) an

optional-to-optional relationship, (b) an optional-to-mandatory relationship, (c) a

mandatory-to-optional relationship, and (d) a mandatory-to-mandatory relation-

ship. Illustrate your answer by using IE Crows Foot E-R diagrams.

5.21 Explain the meaning of the term intersection table.

5.23 For your answers to questions 5.20, 5.21, and 5.22, describe a method for obtaining

the children for one of the entities in the original data model, given the primary key

of the table based on the second entity. Also, describe a method for obtaining the

children for the second entity, given the primary key of the table based on the first

entity.

5.25 Why is it not possible to represent N:M relationships with the same strategy used

to represent 1:N relationships?

5.27 Give an example of a 1:N relationship with an ID-dependent weak entity, other

than one shown in this text. Illustrate your answer using an IE Crows Foot E-R

diagram.

5.29 Define the three types of recursive binary relationships and give an example of

each, other than the ones shown in this text.