SUMMER EXAMINATIONS 2013

Transcription

1 SUMMER EXAMINATIONS 2013 CSY202913N MODULE TITLE Database Technology 1 LEVEL TIME ALLOWED Five Two Hours Instructions to students: Enter your student number not your name on all answer booklets. You are expected to answer three questions from the five. All questions are equally weighted. Where a question has more than one part the division of marks is stated. Begin each answer in a separate booklet; label each booklet clearly with the number of the question you are answering. Neither books nor notes may be taken into the examination. No. of Pages 6 No. of Questions 5 Page 1 of 6

2 Answer THREE questions out of FIVE. Question 1 a) Explain the following concepts of relational model, use example table(s) to illustrate each of them. i) Candidate key; (4 marks) ii) Primary key; (4 marks) iii) Foreign key; (4 marks) iv) Composite key; (4 marks) b) i) When designing table definitions for use in a relational database there are several important factors to consider. Poorly designed tables may lead towards later problems of data integrity. Explain what you believe are the essential things to consider under the following headings when designing such table definitions. Illustrate your answer with well-chosen examples. Naming conventions Data types Constraints (3 marks) (4 marks) (4 marks) ii) During creation of tables, referential actions can be specified on the referenced candidate key. Use an example to explain the use of ON UPDATE CASCADE. (6 marks) Question 2 Appendix A (on page 6) is the database schema for item ordering. Some example data records are shown for each table, but the real tables would obviously have many such records. Write appropriate SQL commands, which would enable someone to perform the following operations. a) Insert a new customer record. (5 marks) b) Display the names of the Customers who live in Kettering. (5 marks) Page 2 of 6

3 Question 2 continued. c) Display details of customers' orders placed during 2009; (5 marks) d) Display details of customers whose first name begins with J; (6 marks) e) Display the names of the customers and the sum of the order totals they have placed; (7 marks) f) Amend the unitprice of WIDGET from 1.5 to 2. (5 marks) Question 3 Read the following ERD carefully, and perform the following tasks: a) Resolve the many-to-many relationship and redraw above ERD. (13 marks) b) Implement the resolved ERD into relational database tables. Make sure the keys (e.g., primary key, foreign keys) are used properly. You might need some arbitrary data in each of the tables for better illustration. (20 marks) Page 3 of 6

4 Question 4 The table below is information about a dental appointment. a) The table is susceptible to update anomalies. Provide examples of insertion, deletion, and update anomalies. (10 marks) b) Identify the functional dependencies represented by the attributes shown in the table. (10 marks) c) Describe and illustrate the process of normalising the table to 3NF. Identify primary and foreign keys in your relations. Relations in each form should be in the following format: Relation (attribute1, attribute2, attribute3 ), where attribute1 is the primary key. (13 marks) Page 4 of 6

5 Question 5 Draw an Entity Relationship Diagram (ERD), which corresponds to the following information. You should use an appropriate notation to represent the various entities and their relationships. You should list any assumptions, which you believe are essential additions to the information given. Doodles is a child daycare centre. A parent registers their child or children at the school using a registration form. A parent can submit more than one registration form. Each room in the daycare is assigned an age group. For example an infant is under 1 year of age and toddlers are from 1 to 3 years of age. A child is assigned to a room based on their age and availability of space. A room may be assigned one or more employees. An employee can only be assigned to one room. The minimum number of employees required for a room is determined by the number of children assigned to the room and the child:staff ratio identified by the government. For example one employee can care for 5 infants or 8 toddlers. END OF QUESTIONS APPENDIX A FOR QUESTION 2 FOLLOWS OVERLEAF Page 5 of 6

6 APPENDIX A (This information relates to Question 2) Table: Customer custid firstname lastname address town JANE GREY 67 Clock Ave, Lei Northampton JOHN SMITH 1 High Street, Kettering GLADYS WIBBLE 32 New Road Northampton Primary key: CustId Table: CustomerOrder orderid orderdate custid Primary key: orderid Foreign key: custid references Customer(custId) Table: StockItem itemid description stocklevel unitprice 776 WIDGET GROMMIT DEVICE Primary key: itemid Table: OrderItem orderid itemid quantity Primary key: (orderid, itemid) Foreign key: orderid references CustomerOrder(orderId) Foreign key: itemid references StockItem(itemId) END OF PAPER Page 6 of 6