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  
 

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 5. 
 A deadlock occurs when  
 

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

 Correct answer is  (d)  

 Your score on this question is: 5.00  
 

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 6. 
 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) A transaction is partially done if the system crashes in the middle of its execution.
 (b) 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.
 (c) 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.
 (d) Transactions either complete, committing all changes to the DBMS, or rollback, resetting the DBMS to a state just prior to a transaction's execution.  

 Correct answer is  (d)  

 Your score on this question is: 5.00  
 

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 7. 
 A collision occurs in hashing when the bucket in which the record to be _____  
 

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

 Correct answer is  (b)  

 Your score on this question is: 5.00  
 

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 8. 
 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) The growing phase ends shortly after the start of the transaction when all locks for the transaction must be acquired.
 (c) The growing phase must be in the first half of the transaction and the shrinking phase must be in the second half.
 (d) There is a plateau phase when locks are neither released nor acquired; this phase comes between the growing phase and the shrinking phase.  

 Correct answer is  (a)  

 Your score on this question is: 5.00  
 

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 9. 
 In a two-phase locking protocol, a transaction _____ downgrade a write lock to a read lock _____.  
 

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

 Correct answer is  (b)  

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

 Correct answer is  (c)  

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

 Correct answer is  (b)  

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

  (a) owner
 (b) vector
 (c) link
 (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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 13. 
 In a hierarchical database, data records are represented using which of the following data structures?  
 

  (a) Arrays
 (b) Hash tables
 (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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 14. 
 Small, highly focused databases at the departmental level that are used to build enterprise-wide data warehouses are known as  
 

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

 Correct answer is  (d)  

 Your score on this question is: 5.00  

 Feedback: 
   
5.2#Issues and Categories of Data Warehouses
 
 

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 15. 
 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) Condensing the view in all the dimensions
 (c) Deriving a coarse-grained view, i.e., a summarized view along a particular dimension
 (d) Viewing along a different dimension  

 Correct answer is  (c)  

 Your score on this question is: 5.00  
 

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 16. 
 To retrieve data from a hierarchical database, program logic for performing _____ must be available.  
 

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

 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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 17. 
 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) I only
 (c) None
 (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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 18. 
 Which of the following types of databases store data in tables and represent relationships using foreign keys?  
 

  (a) Hierarchical databases
 (b) Relational databases
 (c) Object-oriented databases
 (d) Network 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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 19. 
 Which of the following collections allows duplicate elements? 
set 
multiset 
list 
 
 

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

 Correct answer is  (a)  

 Your score on this question is: 5.00  
 

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 20. 
 In a network database, a binary one-to-many relationship is typically represented using a  
 

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

 Correct answer is  (d)  

 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: 95.00 

 ? Copyright 2004 iCarnegie, Inc. All rights reserved.  





Your performance was as follows: 

 You took 6 minutes on this assessment from Sat Apr 28 08:34:39 UTC+0800 2007 to Sat Apr 28 08:40:09 UTC+0800 2007. 

 Total score: 100.00 
 
 

 

 1. 
 An E-Commerce system consists of the following components. Which of these same components must be included in a database? 
The data, such as information about the goods available for sale, customers, orders placed, shipping information, etc. 
A database must include a collection of programs that control the data, such as programs to create, maintain, and manipulate the data. These programs can be easily used to create, maintain, and manipulate data in other domains. 
A database must include a collection of programs that operate on the data, but are specific to the E-commerce system. These programs enable users to browse through the store-items, place orders, track shipping, etc. 
 
 

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

 Correct answer is  (a)  

 Your score on this question is: 14.29  

 Feedback: 
   Database refers to just the data  
 



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 2. 
 In a database system, whose responsibility is it to provide data consistency?  
 

  (a) the DBMS's
 (b) the user's
 (c) the database administrator's
 (d) the application programmer's  

 Correct answer is  (a)  

 Your score on this question is: 14.29  
 

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 3. 
 An E-Commerce system consists of the following components. Which of the same components must be included in a database management system? 
The data, such as information about the goods available for sale, customers, orders placed, shipping information, etc. 
A collection of programs must be included that control the data, such as programs to create, maintain, and manipulate the data. These programs can be easily used to create, maintain, and manipulate data in other domains, such as in a library information system. 
A collection of programs that operate on the data, but are specific to the E-commerce system. These programs enable users to browse through the store-items, place orders, track shipping, etc. 
 
 

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

 Correct answer is  (c)  

 Your score on this question is: 14.29  

 Feedback: 
   A DBMS refers to just the set of general-purpose programs to control data.  
 

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 4. 
 An E-Commerce system consists of the following components. Which of these same components will constitute a database system? 
The data, such as information about the goods available for sale, customers, orders placed, shipping information, etc. 
A collection of programs that control the data, such as programs to create, maintain, and manipulate the data constitutes a database system. These programs can be easily used to create, maintain, and manipulate data in other domains such as in a library information system. 
A collection of programs that operate on the data, but are specific to the E-commerce system, constitutes a database system. These programs enable users to browse through the store-items, place orders, track shipping, etc. 
 
 

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

 Correct answer is  (c)  

 Your score on this question is: 14.29  

 Feedback: 
   A database system includes the data, the DBMS, and the application-specific programs that operate on that data.  
 

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 5. 
 An E-Commerce database contains data about customers, products, orders, system response times, etc. Which of the following can be specified as integrity constraints in an E-Commerce database system? 
No two products can have the same product ID. 
The DBMS response time for all Web requests should be at most 2 seconds. 
A customer order cannot have more than one shipping address. 
 
 

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

 Correct answer is  (a)  

 Your score on this question is: 14.29  

 Feedback: 
   The constraints I, II and III specify the application semantics of the data captured in the E-Commerce database. Constraint III, although it seems contrary to common sense, is not something that can be prohibited by the DBMS because the DBMS is general purpose. The response time of the DBMS cannot be enforced by the DBMS. It depends on factors such the processor speed, memory available, etc.  
 

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 6. 
 A database is needed for which of the following application scenarios? 
A video store that needs to keep track of data about members, about videos carried by the store, about videos rented by members, as well as data concerning borrow-date, return-date, and payment information. 
In the human resources department of a company, information about employees, their titles, their salaries and sick days, and about vacation days taken by each employee. 
A computer-simulated video game which needs to calculate and display, the physical (x, y) location of each actor in the game, the speed with which they are moving at the current instant, the direction in which they are moving, the action they are performing, the angle at which the game-player is viewing the scene. 
 
 

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

 Correct answer is  (d)  

 Your score on this question is: 14.29  
 

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 7. 
 The physical storage structure will be _____ to the application programmer in a database approach, and will be _____ to the application programmer in a file system approach.  
 

  (a) hidden, hidden
 (b) visible, visible
 (c) hidden, visible
 (d) visible, hidden  

 Correct answer is  (c)  

 Your score on this question is: 14.29  

 Feedback: 
   The layer of abstraction offered by a DBMS hides the physical storage structure from the application programmer.  
 

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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 7 minutes on this assessment from Thu Mar 29 09:33:37 UTC+0800 2007 to Thu Mar 29 09:40:34 UTC+0800 2007. 

 Total score: 100.00 
 
 

 

 1. 
 An E-Commerce system consists of the following components. Which of the same components must be included in a database management system? 
The data, such as information about the goods available for sale, customers, orders placed, s