11. | What action does ⋈ operator perform in relational algebra |
Answer: (a).Output specified attributes from all rows of the input relation and remove duplicate tuples from the output
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12. | What does the “x” operator do in relational algebra? |
Answer: (c).Output all pairs of rows from the two input relations (regardless of whether or not they have the same values on common attributes)
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13. | An attribute is a __________ in a relation. |
Answer: (b).Column
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14. | What is the method of specifying a primary key in a schema description? |
Answer: (d).By underlining it using a bold line
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15. | Statement 1: A tuple is a row in a relation Statement 2: Existence of multiple foreign keys in a same relation is possible |
Answer: (a).Both the statements are true
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16. | Choose the option that correctly explains in words, the function of the following relational algebra expression: σyear≥2009 (book ⋈ borrow) |
Answer: (b).Selects all the tuples from the natural join of book and borrow wherever the year is lesser than 2009
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17. | State true or false: If a relation consists of a foreign key, then it is called a referenced relation of the foreign key dependency. |
Answer: (b).False
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18. | Which of the following is not a feature of a good relational design? |
Answer: (d).Allowing redundancy of attributes
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19. | The dependency rules specified by the database designer are known as _______ |
Answer: (c).Functional dependencies
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20. | If the decomposition is unable to represent certain important facts about the relation, then such a decomposition is called as? |
Answer: (b).Lossy decomposition
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