8.1 1. In Figure 8.6, why is BUILDING an entity and not an attribute of another

Question

8.1

1. In Figure 8.6, why is BUILDING an entity and not an attribute of another entity? Because BUILDING is needed for Student, Course and Instructor entities.

2. Why is the room_number attribute attached to the lives in relationship rather than the STUDENT entity? The room_number attribute indicates the room number which

3. What will make you decide whether an attribute should be connected to ENTITYA or ENTITYB or on the relationship connecting ENTITYA and ENTITYB?

4. Why are all the lines leaving BUILDING (on Figure 8.6) single lines (partial participation)?

5. According to Figure 8.6, does a student have to enroll in a course?

6. According to Figure 8.6, how many courses can an instructor teach?

7. According to Figure 8.6, does an instructor have to teach a course?

8. According to Figure 8.6, does a course have to be taught by an instructor?

9. According to Figure 8.6, a course can be taught by how many instructors?

8.2

1. What is a recursive relationship?

2. What would you look for if you are trying to see if a relationship is recursive?

8.3

1. What lower bound of cardinality does full participation imply?

2. What does a min/max ratio of (1,1) between two entities imply?

3. What kind of participation ratio (full participation or partial participation) does a min/max ratio of (0,1) imply?

8.4

1. Map the recursive relationship shown in Figure 8.14 to a relational database and show some sample data.

2. If Figure 8.14 was a M:N relationship, how would you map this recursive relationship to a relational database? Show the mapping with some sample data.

Ch. 8 exercises

room number student name major Lives in L Student student ID M enroll maintenance Supervisor time book occupancy course name Course class Building section number M. bldg number sq. ft teach terminal degree institution instructor ID room number M office Instructor office hours instructor name FIGURE 8.6 ER diagram showing a STUDENTICOURSE/INSTRUCTOR/BUILDING database.

Explanation / Answer

8.2

1.For instance, the entity could be PERSON. associate attribute of the entity could be MOTHER, that could be a PERSON itself. A algorithmic relationship has been outlined as a result of one row within the PERSON table refers to a different row within the same PERSON table.

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