BSc (Hons) in Computer Applications. Examinations for / Semester 1

Transcription

1 BSc (Hons) in Computer Applications Cohort: BCA/07A/PT Examinations for / Semester 1 MODULE: ADVANCED DATABASE MANAGEMENT MODULE CODE: DBT2102 Duration: 2 Hours and 30 Minutes Instructions to Candidates: 1. Answer any four questions. 2. Questions may be answered in any order but your answers must show the question number clearly. 3. Always start a new question on a fresh page. 4. All questions carry equal marks. 5. Total marks 100. This question paper contains 5 questions and 6 pages. Page 1 of 6

2 QUESTION 1: (25 MARKS) Consider the following relational schema that correspond to a part of the database for a computer training college, which offers a variety of IT courses: STUDENT(S#, S_Name, S_DOB, S_Address) COURSE(C#, C_Name, StartDate, EndDate, Fee, D#) DEPARTMENT(D#, D_Name, D_Location) GRADE(S#, C#, Grade, Date_of_Grade) The following assumption are made with regard to the size of each relation: The STUDENT relation contains 1000 records The COURSE relation contains 100 records The DEPARTMENT relation contains 10 records The GRADE relation contains 5000 records There are no more than 50 students in any one course It is possible to hold up to 50 records for an intermediate relation in the main memory. Discuss the objective of query optimisation in a database system, and briefly describe various stages involved in the query optimisation process. [8 Marks] Formulate the following query using correct SQL syntax: Find the names and numbers of all the students who have attended the course entitled E-Commerce [2 Marks] (c) Provide two possible options to evaluate the above query. Express each of these options in relational algebra and clearly show all the steps required in the evaluation of the query. (d) For each of the options identified in (c) above, calculate the number of total tuple input/output operations required for each step. Recommend the best options based on the results [11 Marks] Page 2 of 6

3 QUESTION 2: (25 MARKS) In the context of concurrency control for a multi-transaction database system, briefly discuss the concept of lock and deadlock, and their relationship. [8 Marks] Consider the following two interleaved transactions A and B which might occur in a database system for a bank. Mr Smith s bank account, with an initial balance of $1000, is being updated simultaneously by two transactions A and B in the order shown below: 1. Transaction A retrieves the account balance 2. Transaction A transfer out $300 from the account and updates the account balance. 3. Transaction B retrieves the account balance. 4. Transaction B transfer $200 into the account 5. Transaction A executes a rollback. 6. Transaction B commits the transaction. Answer the following questions: (i) Show the step-by-step changes to the account balance and the final balance of the account, if transaction A and B were performed according to the sequence shown above. (ii) Show the step-by-step changes to the account balance and the final balance of the account, if transactions A and B were performed in a serial sequence (i.e., Transaction A completes all its operations before Transaction B starts). (iii) Identify the type of concurrency problem occurred in the transaction sequence used for (i) above, and explain how the problem arises. [2 Marks] (iv) Provide a step-by-step solution using locking to show how the two transactions would be executed, if appropriate concurrency control were applied to the system. [7 Marks] Page 3 of 6

4 QUESTION 3: (25 MARKS) A distributed database system is defined as: a distributed database system consists of a collection of sites, connected together via some kind of communications network, in which: a. Each site is a full database system site in its own right, but b. The sites have agreed to work together so that a user at any site can access data anywhere in the network exactly as if the data were all stored at the user s own site. Outline the four advantages and three problems in using distributed database systems. [7 Marks] Briefly discuss why data fragmentation could be useful in such distributed database systems, and explain each of the following fragmentation rules: Completeness Reconstruction Disjointness [8 Marks] (c) Demonstrate in detail how these rules are enforced when performing horizontal and vertical fragmentation, by using the STUDENT relation given below: [10 Marks] STUDENT SNo SName SAdress SType Registration SCity S1355 Owen 20 Small Street Full Time London S0072 Clare 12 Royal Street Part Time London S4813 Tony 89 Oak Street Full Time Oxford S0379 Peter 54 Green Avenue Distance Learning Oxford S9947 Spencer 11 Hilton Road Part Time London S2223 Howard 34 Colinton Road Distance Learning London Page 4 of 6

5 QUESTION 4: (25 MARKS) Discuss the main advantages of object-oriented database systems (OODBMS) which, in your opinion, have contributed to OODBMSs popularity in recent years. Your discussion should include identifying inadequacies of the existing relational database technology. Give example of One Advanced Database Applications and explain why this application is not suitable for a relational database. [15 Marks] Discuss the main features of a deductive database system, and contrast it with a relational database system. Your discussion should include identifying the role of logic programming in a deductive database. (c) In the context of deductive databases, explain the following concepts: Extensional database Intentional database Recursive query [6 Marks] Page 5 of 6

6 QUESTION 5: (25 MARKS) What are decision support systems, and what role do they play in the business environment? [3 Marks] Data warehousing is defined as a subject-oriented, integrated, time-variant, non-volatile collection of data in support of management s decision making process. (i) Define the term subject-oriented and support your answer with appropriate examples. (ii) Describe the three important differences that exist between an application oriented system and a subject oriented system. [6 Marks] (c) Data mining is a knowledge discovery process of automated extraction of hidden predictive information from large databases. (i) Data mining being relatively a new technology, what advantages would a Commercial Bank achieved for implementing such a technique. Provide relevant Examples (ii) To better exploit data mining what are the pre-requisites for a data warehouse. (iii) Discuss the two critical factors which can affect success with the application of data mining technology. ***END OF QUESTION PAPER*** Page 6 of 6