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49. According to Codd’s rule of relational databases, application programs and ad hoc facilities are logically unaffected when changes are made to the table structures that preserve the original table values (changing order of columns or inserting columns). a. distribution independence b. logical data independence c. comprehensive data sublanguage d. integrity independence ANSWER: b DIFFICULTY: Difficulty: Moderate REFERENCES: 3-9 Codd’s Relational Database Rules LEARNING OBJECTIVES: 03.02 - Identify the relational model’s basic components and explain the structure, contents, and characteristics of a relational table 50. According to Codd's rule of relational databases, if the system supports low-level access to the data, users must not be allowed to bypass the integrity rules of the database. a. nonsubversion b. information c. guaranteed access d. view updating ANSWER: a DIFFICULTY: Difficulty: Moderate REFERENCES: 3-9 Codd’s Relational Database Rules LEARNING OBJECTIVES: 03.02 - Identify the relational model’s basic components and explain the structure, contents, and characteristics of a relational table Completion 51. A table is also called a(n) because the relational model’s creator, E. F. Codd, used the two terms as synonyms. ANSWER: relation DIFFICULTY: Difficulty: Easy REFERENCES: 3-1a Tables and Their Characteristics LEARNING OBJECTIVES: 03.02 - Identify the relational model’s basic components and explain the structure, contents, Copynght Cengage Leaming. Powered by Cognero. Page 10 Chapter 03: The Relational Database Model and characteristics of a relational table 52. In a relational table, each column has a specific range of values known asthe ____ domain. ANSWER: attribute DIFFICULTY: Difficulty: Easy REFERENCES: 3-1a Tables and Their Characteristics LEARNING OBJECTIVES: 03.02 - Identify the relational model’s basic components and explain the structure, contents, and characteristics of a relational table 53. A primary key is a(n) key chosen to be the primary means by which rows of a table are uniquely identified. ANSWER: candidate DIFFICULTY: Difficulty: Easy REFERENCES: 3-1a Tables and Their Characteristics LEARNING OBJECTIVES: 03.02 - ldentify the relational model’s basic components and explain the structure, contents, and characteristics of a relational table 54.In arelational model, _____ are used to establish relationships among tables and to ensure the integrity of the data. ANSWER: keys DIFFICULTY: Difficulty: Easy REFERENCES: 3-2 Keys LEARNING OBJECTIVES: 03.02 - Identify the relational model’s basic components and explain the structure, contents, and characteristics of a relational table 55. To avoid nulls, some designers use special codes, known as _____ . to indicate the absence of some value. ANSWER: flags DIFFICULTY: Difficulty: Easy REFERENCES: 3-3 Integrity Rules LEARNING OBJECTIVES: 03.02 - Identify the relational model’s basic components and explain the structure, contents, and characteristics of a relational table 56. The relational operators have the property of ____: that is, the use of relational algebra operators on existing relations (tables) produces new relations. ANSWER: closure DIFFICULTY: Difficulty: Easy REFERENCES: 3-4b Relational Set Operators LEARNING OBJECTIVES: 03.03 - Use relational database operators to manipulate relational table contents 57. PRODUCT yields all possible pairs of rows from two tables, also known asthe _____ product. ANSWER: Cartesian DIFFICULTY: Difficulty: Moderate REFERENCES: 3-4b Relational Set Operators LEARNING OBJECTIVES: 03.03 - Use relational database operators to manipulate relational table contents 58. is the real power behind the relational database, allowing the use of independent tables linked by common attributes. ANSWER: JOIN DIFFICULTY: Difficulty: Easy @ O 2