潜龙勿用1.txt

ssd7数据库练习选择题1-4答案

  (a) II and III only
 (b) I only
 (c) III only
 (d) I and II only  

 Correct answer is  (b)  

 Your score on this question is: 5.00  
 

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 8. 
 The undo action undoes the effects of a(n) _____ transaction, and the redo action redoes the effects of a(n) _____ transaction.  
 

  (a) aborted, aborted
 (b) committed, aborted
 (c) committed, committed
 (d) aborted, committed  

 Correct answer is  (d)  

 Your score on this question is: 5.00  
 

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 9. 
 Which of the following is true about the growing phase and the shrinking phase of a strict two-phase locking protocol?  
 

  (a) The growing phase must be in the first half of the transaction and the shrinking phase must be in the second half.
 (b) There is a plateau phase when locks are neither released nor acquired; this phase comes between the growing phase and the shrinking phase.
 (c) The growing phase ends just before commit.
 (d) The growing phase ends shortly after the start of the transaction when all locks for the transaction must be acquired.  

 Correct answer is  (c)  

 Your score on this question is: 5.00  
 

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 10. 
 An index file is usually used to index ______ of the data file.  
 

  (a) most fields
 (b) all fields
 (c) two fields
 (d) one field  

 Correct answer is  (d)  

 Your score on this question is: 0.00  
 

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 11. 
 In a hierarchical database, a single tree can accommodate which of the following types of binary relationships?

One-to-one relationships 
One-to-many relationships 
Many-to-many relationships 
 
 

  (a) I only
 (b) I, II, and III
 (c) I and II only
 (d) None  

 Correct answer is  (c)  

 Your score on this question is: 5.00  

 Feedback: 
   
See section 5.1.3, subsection "Hierarchical Data Model," in the course notes.
 
 

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 12. 
 What is a roll-up operation in a data warehouse application?  
 

  (a) Condensing the view in all the dimensions
 (b) Viewing along a different dimension
 (c) Deriving a coarse-grained view, i.e., a summarized view along a particular dimension
 (d) Deriving a fine-grained view, i.e., a disaggregated view along a particular dimension  

 Correct answer is  (c)  

 Your score on this question is: 5.00  
 

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 13. 
 In a network database, data records are represented using which of the following data structures?  
 

  (a) Graphs
 (b) Arrays
 (c) Matrices
 (d) Hash tables  

 Correct answer is  (a)  

 Your score on this question is: 5.00  

 Feedback: 
   
See section 5.1.3, subsection "Network Data Model," in the course notes.
 
 

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 14. 
 To retrieve data from a hierarchical database, program logic for performing _____ must be available.  
 

  (a) polymorphism
 (b) relational joins
 (c) decomposition
 (d) navigation  

 Correct answer is  (d)  

 Your score on this question is: 5.00  

 Feedback: 
   
See section 5.1.3, subsection "Hierarchical Data Model," in the course notes.
 
 

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 15. 
 Which of the following collections allows duplicate elements? 
set 
multiset 
list 
 
 

  (a) II only
 (b) II and III only
 (c) III only
 (d) I, II, and III  

 Correct answer is  (b)  

 Your score on this question is: 5.00  
 

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 16. 
 Small, highly focused databases at the departmental level that are used to build enterprise-wide data warehouses are known as  
 

  (a) virtual data warehouses
 (b) data marts
 (c) data cubes
 (d) hypercubes  

 Correct answer is  (b)  

 Your score on this question is: 5.00  

 Feedback: 
   
5.2#Issues and Categories of Data Warehouses
 
 

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 17. 
 In a network database, the first record of an ordered linked list that represents a one-to-many relationship is called a(n)  
 

  (a) owner
 (b) link
 (c) vector
 (d) intermediary  

 Correct answer is  (a)  

 Your score on this question is: 5.00  

 Feedback: 
   
See section 5.1.3, subsection "Network Data Model," in the course notes.
 
 

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 18. 
 In a network database, a binary one-to-many relationship is typically represented using a  
 

  (a) binary tree
 (b) sparse matrix
 (c) linked list
 (d) hash table  

 Correct answer is  (c)  

 Your score on this question is: 5.00  

 Feedback: 
   
See section 5.1.3, subsection "Network Data Model," in the course notes.
 
 

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 19. 
 In a hierarchical database, data records are represented using which of the following data structures?  
 

  (a) Hash tables
 (b) Arrays
 (c) Matrices
 (d) Trees  

 Correct answer is  (d)  

 Your score on this question is: 5.00  

 Feedback: 
   
See section 5.1.3, subsection "Hierarchical Data Model," in the course notes.
 
 

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 20. 
 Which of the following statements is (are) typically true of hierarchical databases?

They are navigated using preorder traversals. 
Their users must be aware of the databases’ internal tree structures. 
 
 

  (a) I and II
 (b) I only
 (c) None
 (d) II only  

 Correct answer is  (a)  

 Your score on this question is: 5.00  

 Feedback: 
   
See section 5.1.3, subsection "Hierarchical Data Model," in the course notes.
 
 

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 Go to top of assessment.  

 Total score: 80.00 

 ? Copyright 2004 iCarnegie, Inc. All rights reserved.  

A shared lock on a data item represents permission to perform which of the operations, read and write, on the data item?  
 

  (a) Write only
 (b) Read only
 (c) Both read and write
 (d) Neither read nor write  

 Correct answer is  (b)  

 Your score on this question is: 5.00  
 



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 2. 
 In a two-phase locking protocol, a transaction _____ upgrade a read lock to a write lock _____.  
 

  (a) cannot, under any circumstances
 (b) can, in the growing phase only
 (c) cannot, in the shrinking phase o
 (d) can, under all circumstances  

 Correct answer is  (b)  

 Your score on this question is: 0.00  
 

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 3. 
 Hash files use a hash function to map a _____ to a(n) _____  
 

  (a) hash value, address where the key may be found
 (b) key value, address where the key may be found
 (c) key value, address where the hash value may be found
 (d) hash value, key where the address may be found  

 Correct answer is  (b)  

 Your score on this question is: 5.00  
 

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 4. 
 A collision occurs in hashing when the bucket in which the record to be _____  
 

  (a) deleted has exactly one record
 (b) stored is full
 (c) deleted is full
 (d) stored has at least one other record  

 Correct answer is  (b)  

 Your score on this question is: 5.00  
 

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 5. 
 Which of the following is true about the effects of a transaction as seen by an external user who does not participate in the transaction?  
 

  (a) During recovery from a crash, the DBMS may decide to undo the effects of a committed transaction and hence the effects will not be seen by the user after the undo.
 (b) Transactions either complete, committing all changes to the DBMS, or rollback, resetting the DBMS to a state just prior to a transaction's execution.
 (c) A transaction is partially done if the system crashes in the middle of its execution.
 (d) During recovery from a crash, the DBMS may decide to redo the effects of an aborted transaction and hence the effects will be seen by the user after the redo.  

 Correct answer is  (b)  

 Your score on this question is: 5.00  
 

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 6. 
 A file is fully inverted if and only if  
 

  (a) none of the fields are indexed
 (b) all the fields are indexed
 (c) the records are stored in the descending order of the primary key
 (d) the data files point to the index files  

 Correct answer is  (b)  

 Your score on this question is: 5.00  
 

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 7. 
 Which concurrency control protocols perform best in all situations?  
 

  (a) two-phase locking protocols
 (b) pessimistic protocols
 (c) optimistic protocols
 (d) none  

 Correct answer is  (d)  

 Your score on this question is: 5.00  
 

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 8. 
 Hashing works best for which of the following searches? 
equality searches 
range searches 
substring searches 
 
 

  (a) I only
 (b) I and II only
 (c) III only
 (d) II and III only  

 Correct answer is  (a)  

 Your score on this question is: 5.00  
 

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 9. 
 In a two-phase locking protocol, what happens when a transaction requests a conflicting lock?  
 

  (a) The transaction proceeds without acquiring the lock.
 (b) The transaction is aborted immediately.
 (c) The transaction immediately acquires the lock from the current lock-holder.
 (d) The transaction is blocked to acquire the lock.  

 Correct answer is  (d)  

 Your score on this question is: 5.00  
 

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 10. 
 The undo action undoes the effects of a(n) _____ transaction, and the redo action redoes the effects of a(n) _____ transaction.  
 

  (a) aborted, committed
 (b) committed, aborted
 (c) committed, committed
 (d) aborted, aborted  

 Correct answer is  (a)  

 Your score on this question is: 5.00  
 

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 11. 
 Which of the following statements is (are) typically true of hierarchical databases?

They are navigated using preorder traversals. 
Their users must be aware of the databases’ internal tree structures. 
 
 

  (a) None
 (b) I only
 (c) II only
 (d) I and II  

 Correct answer is  (d)  

 Your score on this question is: 5.00  

 Feedback: 
   
See section 5.1.3, subsection "Hierarchical Data Model," in the course notes.
 
 

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 12. 
 In a hierarchical database, data records are represented using which of the following data structures?  
 

  (a) Trees
 (b) Arrays
 (c) Matrices
 (d) Hash tables  

 Correct answer is  (a)  

 Your score on this question is: 5.00  

 Feedback: 
   
See section 5.1.3, subsection "Hierarchical Data Model," in the course notes.
 
 

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 13. 
 In a network database, the first record of an ordered linked list that represents a one-to-many relationship is called a(n)  
 

  (a) link
 (b) vector
 (c) owner
 (d) intermediary  

 Correct answer is  (c)  

 Your score on this question is: 5.00  

 Feedback: 
   
See section 5.1.3, subsection "Network Data Model," in the course notes.