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  1. --------------------------
  2. Post Title 'DBMS Assignment-1 Answers'
  3. Post by user 'Adusumilli-Uday-Kumar'
  4. Post encryped with secure 256-bit MD5 Encryption
  5. Post accesable only VIA link
  6. Post will Expire on '3-OCT-2017'
  7. --------------------------
  8.  
  9.  
  10.  
  11. ----
  12. 1. List the charecterristics of Database Approach.
  13. Ans.
  14. In traditional file processing, each user defines and implements the files needed for a specific software application as part of programming the application.
  15. In the database approach, a single repository maintains data that is defined once and then accessed by various users. In file systems, each application is free to name data elements independently. In contrast, in a database, the names or labels of data are defined once, and used repeatedly by queries, transactions, and applications.
  16.  
  17. The main characteristics of the database approach versus the file-processing
  18. approach are the following:
  19. - Self-describing nature of a database system
  20. - Insulation between programs and data, and data abstraction
  21. - Support of multiple views of the data
  22. - Sharing of data and multiuser transaction processing
  23.  
  24. ----
  25. 2. Discuss the advantages of using DBMS Approach.
  26. Ans.
  27. 1) Controlling Redundancy:
  28. In traditional software development utilizing file processing, every user group maintains its own files for handling its data-processing applications. Other groups may further duplicate some or all of the same data in their own files. This redundancy in storing the same data multiple times leads to several problems.
  29. In the database approach, the views of different user groups are integrated during database design. This is known as data normalization, and it ensures consistency and saves storage space. However, in practice, it is sometimes necessary to use controlled redundancy to improve the performance of queries.
  30.  
  31. 2) Restricting Unauthorized Access:
  32. When multiple users share a large database, it is likely that most users will not be authorized to access all information in the database.
  33.  
  34. 3) Providing Persistent Storage for Program Objects:
  35. Databases can be used to provide persistent storage for program objects and data structures. This is one of the main reasons for object-oriented database systems.
  36.  
  37. 4) Providing Storage Structures and Search:
  38. Techniques for Efficient Query Processing
  39. Database systems provide capabilities for efficiently executing queries and updates. Because the database is typically stored on disk, the DBMS must provide specialized data structures and search techniques to speed up disk search for the desired records.
  40.  
  41. 5) Providing Backup and Recovery:
  42. A DBMS provides facilities for recovering from hardware or software failures. The backup and recovery subsystem of the DBMS is responsible for recovery.
  43.  
  44. 6) Providing Multiple User Interfaces:
  45. Because many types of users with varying levels of technical knowledge use a database, a DBMS provides a variety of user interfaces. These include query languages for casual users, programming language interfaces for application programmers, forms and command codes for parametric users.
  46.  
  47. 7) Representing Complex Relationships among Data
  48. A database may include numerous varieties of data that are interrelated in many ways.
  49.  
  50. 8) Enforcing Integrity Constraints
  51. Most database applications have certain integrity constraints that must hold for the data. A DBMS provides capabilities for defining and enforcing these con-1.6 Advantages of Using the DBMS Approach straints.
  52.  
  53. ----
  54. 3. With a neat diagram, explain the 3 Schema Architechure.
  55. Ans. The goal of the three-schema architecture is to separate the user applications from the physical database. In this architecture, schemas can be defined at the following three levels:
  56.  
  57. 1) The internal level has an internal schema, which describes the physical storage structure of the database. The internal schema uses a physical data model and describes the complete details of data storage and access paths for the database.
  58. 2) The conceptual level has a conceptual schema, which describes the structure of the whole database for a community of users. The conceptual schema hides the details of physical storage structures and concentrates on describing entities, data types, relationships, user operations, and constraints.
  59. 3) The external or view level includes a number of external schemas or user views. Each external schema describes the part of the database that a particular user group is interested in and hides the rest of the database from that user group.
  60.  
  61. Image Link: http://bit.ly/2iNBkgI
  62.  
  63. ----
  64. 4. With a neat diagram, explain the different phases of Database Design.
  65. Ans. We can identify six main phases of the overall database design and implementation process:
  66. 1) Requirements collection and analysis
  67. 2) Conceptual database design
  68. 3) Choice of a DBMS
  69. 4) Data model mapping (also called logical database design)
  70. 5) Physical database design
  71. 6) Database system implementation and tuning
  72.  
  73. The heart of the database design process comprises Phases 2, 4, and 5; we briefly summarize these phases:
  74. - Conceptual database design (Phase 2):
  75. The goal of this phase is to produce a conceptual schema for the database that is independent of a specific DBMS. We often use a high-level data model such as the ER or EER model during this phase.
  76. - Data model mapping (Phase 4):
  77. During this phase, which is also called logical database design, we map (or transform) the conceptual schema from the high-level data model used in Phase 2 into the data model of the chosen DBMS.
  78. - Physical database design (Phase 5):
  79. During this phase, we design the specifications for the stored database in terms of physical file storage structures, record placement, and indexes. This corresponds to designing the internal schema in the terminology of the three-level DBMS architecture.
  80. - Database system implementation and tuning (Phase 6):
  81. During this phase, the database and application programs are implemented, tested, and eventually deployed for service. Various transactions and applications are tested individually and then in conjunction with each other.
  82.  
  83. Image Link: http://bit.ly/2wve6PG
  84.  
  85. ----
  86. 5. Write an ER Diagram for the following:
  87. - Company
  88. - Order
  89. - Library
  90. - Movie
  91. - Bank
  92. Ans.
  93.  
  94. ER Diagram for Company,
  95. Image Link: http://bit.ly/2wvgLsA
  96.  
  97. ER Diagram for Order,
  98. Image Link: http://bit.ly/2ewOTjF
  99.  
  100. ER Diagram for LIbrary,
  101. Image Link: http://bit.ly/2vS3IQm
  102.  
  103. ER Diagram for Movie,
  104. Image Link: http://bit.ly/2iPd7Xq
  105.  
  106. ER Diagram for Bank,
  107. Image Link: http://bit.ly/2ewtbMA
  108.  
  109. ----
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