潜龙勿用1.txt

ssd7数据库练习选择题1-4答案

 Your score on this question is: 5.00  

 Feedback: 
   
5.2#Issues and Categories of Data Warehouses
 
 

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 20. 
 In a network database, the first record of an ordered linked list that represents a one-to-many relationship is called a(n)  
 

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

 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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 Go to top of assessment.  

 Total score: 100.00 

 ? Copyright 2004 iCarnegie, Inc. All rights reserved.

Your performance was as follows: 

 You took 130 minutes on this assessment from Sat Jul 7 09:04:07 UTC+0800 2007 to Sat Jul 7 11:13:54 UTC+0800 2007. 

 Total score: 95.00 
 
 

 

 1. 
 Hashing works best for which of the following searches? 
equality searches 
range searches 
substring searches 
 
 

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

 Correct answer is  (b)  

 Your score on this question is: 5.00  
 



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 2. 
 A deadlock occurs when  
 

  (a) a transaction is aborted and restarted repeatedly
 (b) 2 or more transactions wait indefinitely because each holds the data items of another
 (c) a transaction holding a lock is aborted
 (d) an aborted transaction holding a lock is restarted  

 Correct answer is  (b)  

 Your score on this question is: 0.00  
 

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 3. 
 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 ends just before commit.
 (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 shortly after the start of the transaction when all locks for the transaction must be acquired.
 (d) The growing phase must be in the first half of the transaction and the shrinking phase must be in the second half.  

 Correct answer is  (a)  

 Your score on this question is: 5.00  
 

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 4. 
 Which concurrency control protocols perform best in all situations?  
 

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

 Correct answer is  (a)  

 Your score on this question is: 5.00  
 

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 5. 
 A shared lock on a data item represents permission to perform which of the operations, read and write, on the data item?  
 

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

 Correct answer is  (d)  

 Your score on this question is: 5.00  
 

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 6. 
 Which of the following will a good hash function do?  
 

  (a) spread keys around the file in heaps
 (b) spread keys around the file as evenly as possible
 (c) concentrate keys in one location
 (d) leave gaps in the file at periodic intervals for future growth  

 Correct answer is  (b)  

 Your score on this question is: 5.00  
 

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 7. 
 Which of the following is true about transactions affecting the consistency of a database?  
 

  (a) There are no guarantees that transactions will leave the database in a consistent state.
 (b) A transaction always leaves the database in a consistent state.
 (c) A transaction leaves the database in a consistent state if there is no system crash during the execution of the transaction.
 (d) A transaction leaves the database in a consistent state if the user has not violated any integrity constraints.  

 Correct answer is  (b)  

 Your score on this question is: 5.00  
 

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 8. 
 Which of the following is true about compensating transactions?  
 

  (a) The DBMS cannot automatically write compensating transactions.
 (b) The user can request the DBMS to write compensating transactions automatically.
 (c) The DBMS will automatically write a compensating transaction for each committed transaction.
 (d) The DBMS can automatically write compensating transactions.  

 Correct answer is  (a)  

 Your score on this question is: 5.00  
 

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 9. 
 A collision occurs in hashing when the bucket in which the record to be _____  
 

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

 Correct answer is  (d)  

 Your score on this question is: 5.00  
 

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 10. 
 In a two-phase locking protocol, what happens when a transaction requests a conflicting lock?  
 

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

 Correct answer is  (a)  

 Your score on this question is: 5.00  
 

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 11. 
 In a network database, data records are represented using which of the following data structures?  
 

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

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

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

 Correct answer is  (c)  

 Your score on this question is: 5.00  
 

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 13. 
 Small, highly focused databases at the departmental level that are used to build enterprise-wide data warehouses are known as  
 

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

 Correct answer is  (c)  

 Your score on this question is: 5.00  

 Feedback: 
   
5.2#Issues and Categories of Data Warehouses
 
 

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 14. 
 In a hierarchical database, data records are represented using which of the following data structures?  
 

  (a) Matrices
 (b) Arrays
 (c) Hash tables
 (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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 15. 
 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) II only
 (b) None
 (c) I 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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 16. 
 To retrieve data from a hierarchical database, program logic for performing _____ must be available.  
 

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

 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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 17. 
 Which of the following types of databases store data in tables and represent relationships using foreign keys?  
 

  (a) Network databases
 (b) Relational databases
 (c) Object-oriented databases
 (d) Hierarchical databases  

 Correct answer is  (b)  

 Your score on this question is: 5.00  

 Feedback: 
   
See section 5.1.3, subsection "Relational 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) sparse matrix
 (b) linked list
 (c) binary tree
 (d) hash table  

 Correct answer is  (b)  

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

 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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 20. 
 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.
 
 

--------------------------------------------------------------------------------

 Go to top of assessment.  

 Total score: 95.00 

 ? Copyright 2004 iCarnegie, Inc. All rights reserved.  
  

 

 Your performance was as follows: 

 You took 25 minutes on this assessment from Sat Jul 7 09:00:38 UTC+0800 2007 to Sat Jul 7 09:25:31 UTC+0800 2007. 

 Total score: 95.00 
 
 

 

 1. 
 In a two-phase locking protocol, a transaction _____ upgrade a read lock to a write lock _____.  
 

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

 Correct answer is  (d)  

 Your score on this question is: 5.00  
 



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 2. 
 The undo action undoes the effects of a(n) _____ transaction, and the redo action redoes the effects of a(n) _____ transaction.  
 

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

 Correct answer is  (d)  

 Your score on this question is: 5.00  
 

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 3. 
 How does linear probing solve the problem of collisions in hashing?  
 

  (a) A linear function is used to determine the next spot to search for slots.
 (b) A serial search is performed from the point of collision to find the first available slot.
 (c) The hash file is probed linearly from the start to find the first available slot.
 (d) The hash file is probed linearly from the end to find the first available slot.  

 Correct answer is  (b)  

 Your score on this question is: 5.00  
 

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 4. 
 Which of the following will a good hash function do?  
 

  (a) spread keys around the file as evenly as possible
 (b) concentrate keys in one location
 (c) spread keys around the file in heaps
 (d) leave gaps in the file at periodic intervals for future growth  

 Correct answer is  (a)