Chapter 3 - Relational Model Tutorial 1. What kind of data model is the relational model ? 2. (a) Explain the following terms in the context of the relational data model. Relation Attribute Domain Tuple Degree Cardinality (b) Use the Suppliers-Parts database to provide examples of each (see Appendix 1 of this tutorial). 3. (a) Explain the following terms in the context of the relational data model. Candidate Key Primary Key Foreign Key (b) Use the Suppliers-Parts database to provide examples of each. 4. (a) What is the purpose of nulls and what do they represent ? (b) Is a component of a primary key allowed to accept nulls, why ? (c) What is the term for this constraint ? (d) Use the Suppliers-Parts database to discuss why it is desirable to enforce this constraint. 5. (a) Describe the constraint called referential integrity. (b) What is the purpose of this constraint ? (c) Use the Suppliers-Parts database to discuss why it is desirable to enforce referential integrity. 6. Examine your “course timetable” and try to answer the following questions: (a) Have all data in the timetable interpretations ? (b) Are the data and their interpretations kept together ? (c) Is there any data model behind the data? If so what kind of data model is it and why ? (d) Are the data structured in a relation and why ? (e) How would you re-structure the data according to the rules of the relational data model ? 7. (a) What is a view ? (b) Discuss the difference between a view and a base relation. (c) Explain what happens when a user accesses a database through a view. Appendix 1 Suppliers - Parts Database Suppliers SNo SNam e Status City S1 Smith 20 London S2 Jones 10 Paris S3 Blake 30 Paris S4 Clark 20 London S5 Adams 30 Athens Parts PNo PName Colour Weight City P1 Nut Red 12 London P2 Bolt Green 17 Paris P3 Screw Blue 17 Rome P4 Screw Red 14 London P5 Cam Blue 12 Paris P6 Cog Red 19 London Shipm en ts SNo PNo Qty S1 P1 300 S1 P2 200 S1 P3 400 S1 P4 200 S1 P5 100 S1 P6 100 S2 P1 300 S2 P2 400 S3 P2 200 S4 P2 200 S4 P4 300 S4 P5 400 . Chapter 3 - Relational Model Tutorial 1. What kind of data model is the relational model ? 2. (a) Explain the following terms in the context of the relational data model. Relation Attribute Domain Tuple Degree Cardinality (b). Cog Red 19 London Shipm en ts SNo PNo Qty S1 P1 30 0 S1 P2 200 S1 P3 400 S1 P4 200 S1 P5 100 S1 P6 100 S2 P1 30 0 S2 P2 400 S3 P2 200 S4 P2 200 S4 P4 30 0 S4 P5 400 . 20 London S2 Jones 10 Paris S3 Blake 30 Paris S4 Clark 20 London S5 Adams 30 Athens Parts PNo PName Colour Weight City P1 Nut Red 12 London P2 Bolt Green 17 Paris P3 Screw Blue 17 Rome P4 Screw