dp10_tif_ch03

dp10_tif_ch03 - CHAPTER THREE THE RELATIONAL MODEL AND...

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CHAPTER THREE THE RELATIONAL MODEL AND NORMALIZATION True-False Questions 1. All relations are tables, but not all tables are relations. Answer: True Page: 71 2. A relation is a three-dimensional table. Answer: False Page: 71-73 [And see Figure 3-4] 3. A characteristic of a relation is that the cells of the relation hold a single value. Answer: True Page: 71-73 [And see Figure 3-4] 4. A characteristic of a relation is that the rows of a relation may hold identical values. Answer: False Page: 71-73 [And see Figure 3-4] 5. The columns of a relation are sometimes called "tuples." Answer: False Page: 73-74 {And see Figure 3-7] 6. A tuple is a group of one or more columns that uniquely identifies a row. Answer: False Page: Page: 73-74 {And see Figure 3- 7] 7. Attribute Y is functionally dependent on attribute X if the value of attribute X determines the value of Y. Answer: True Page: 74-75 8. The functional dependency noted as A B, means that the value of A can be determined from the value of B. Answer: False Page: 74 9. In the functional dependency shown as A B, B is the determinant. Answer: False Page: 74 ¶10. Functional dependencies can involve groups of attributes. Answer: True Page: 74-75 11. A determinant of a functional dependency may or may not be unique in a relation. Answer: True Page: 79 12. A row can be uniquely identified by a key. Answer: True Page: 79 13. A key can be composed of a group of attributes taken together. Page 3-1

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Chapter Three The Relational Model and Normalization Answer: True Page: 79 14. It is possible to have a relation that does not have a key. Answer: False Page: 79-80 15. A relation can have only one candidate key. Answer: False Page: 79-80 16. Surrogate keys usually slow performance. Answer: False Page: 80 17. Surrogate keys are normally not shown on forms or reports. Answer: True Page: 80 18. A constraint that requires an instance of an entity to exist in one relation before it can be referenced in another relation is called an insertion anomaly. Answer: False Page: 80-81 19. A referential integrity constraint limits the values of a foreign key. Answer: True Page: 81 20. If a table meets the minimum definition of a relation, it has an effective or appropriate structure. Answer: False Page: 81 21. Undesirable consequences of changing the data in a relation are called "modification anomalies." Answer: True Page: 81 ¶22. A deletion anomaly exists when deleting data about one entity results in the loss of data about another entity. Answer: True Page: 80-81 23. Relations are classified into "normal forms" based on the types of modification anomalies that they are vulnerable to. Answer: True Page: 82-83 [And see Figure 3-10] 24. Any table that meets the definition of a relation is in 2NF. Answer:
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dp10_tif_ch03 - CHAPTER THREE THE RELATIONAL MODEL AND...

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