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8.1 Checkpoint 1. In Figure 8.6, why is BUILDING an entity and not an attribute of another entity? -Building is an entity because of its relationship attribute or the intersection attribute. This is because these kinds of attributes require more than one entity. An example: here students, courses, and instructors, an entity require all this building information and is not specific to a single entity. This is what will create an intersection attribute. 2. Why is the room_number attribute attached to the lives_in relationship rather than the STUDENT entity? -A room number is an intersection attribute, building, and student entities both require a room_number attribute. That is why we added to the “livesin” relationship rather than the STUDENT entity. 3. What will make you decide whether an attribute should be connected to ENTITYA or ENTITYB or on the relationship connecting ENTITYA and ENTITYB? -An attribute, if it is required by a single entity like in Entity A or Entity B, we then can add that attribute to that entity. In some scenarios, attributes may need to be required or belong to more than one entity. If that is the case, we can add to the relationship connection between those entities. 4. Why are all the lines leaving BUILDING (on Figure 8.6) single lines (partial participation)? -It is designed with part participation. This is because for online classes or remote classes BUILDING entity may be null or not required for students, course, or instructor information. 5. According to Figure 8.6, does a student have to enroll in a course? -Yes, a student must be enrolled in a course as it is designed with full participation. 6. According to Figure 8.6, how many courses can an instructor teach? -An instructor can only teach one course according to Figure 8.6. 7. According to Figure 8.6, does an instructor have to teach a course? -No, the instructor is not required to teach a course, because it is designed with part participation.
8. According to Figure 8.6, does a course have to be taught by an instructor? -Yes, a course must be taught by an instructor as it is designed with full participation. 9. According to Figure 8.6, a course can be taught by how many instructors? -Based on Figure 8.6, a course can be taught by multiple instructors since it is designed with M:1. (full participation). 8.2 Checkpoint 1. What is a recursive relationship? -A recursive relationship is a relationship with the same entity or same entity participants with more than once having different roles. 2. What would you look for if you are trying to see if a relationship is recursive? - What to look for when trying to see if a relationship is recursive, is to see if any entity participants have more than one different role. Also, it can only have a partial relationship, but the cardinality can be one-to-one to one-to-many and many-to-many. 8.3 Checkpoint 1. What lower bound of cardinality does full participation imply? - A lower bound of cardinality should have a value of 1. EX; (1,1). Here the lower bound is 1 which means full participation. If the lower bound is zero, this means it is part participation. 3. What does a min/max ratio of (1, 1) between two entities imply? -1:1 (meaning full participation can only have one record in other entities) 4. What kind of participation ratio (full participation or partial participation) does a min/max ratio of (0, 1) imply? - Yes (0,1) does imply. Because partial participation can have only one record in other entities.
8.4 Checkpoint 1. Map the recursive relationship shown in Figure 8.14 to a relational database and show some sample data. *Employee (first_name, middle_name, employee ID, supervisor ID and emailed) Sample Data:
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2. If Figure 8.14 was an M:N relationship, how would you map this recursive relationship to a relational database? Show the mapping with some sample data. SAMPLE DATA:
CHAPTER 8 EXERCISE (8.1) Define and state in precise terms the cardinality and participation in Figure 8.6, the student/course/instructor/building database. Discuss the structural constraints of Figure 8.6. What are the participations? What are the cardinalities? Under which circumstances would the ones depicted be correct or incorrect? 1. Student and Course: Many to Many (M:N) with full participation from both sides. This means that a student can enroll in multiple courses and a course can have multiple students. 2. Instructor and Course: One to Many (1:M) with full participation from the course and partial participation from the instructor. This means that an instructor can teach multiple courses, but a course must be taught by one instructor. 3. Student and Building: Many to Many (M:N) with full participation from the student and partial participation from the building. This means that a student can live in multiple buildings and a building can house multiple students. 4. Course and Building: Many to One (M:1) with full participation from the course and partial participation from the building. This means that a course must be taught in a building, but a building can host multiple courses. 5. Instructor and Building: Many to One (M:1) with full participation from the instructor and partial participation from the building. This means that an instructor can have an office in multiple buildings, but a building can house the office, multiple instructors. **The depicted relationships would be correct. Only if they accurately represent the real-world relationships between students, courses, instructors, and buildings.

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