School of Computing and Information Systems
INFO20003 Database Systems
SAMPLE EXAM
Reading Time: 15 minutes
Writing time: 120 minutes
This paper has 14 pages including this page
Authorised Materials
Calculators: Casio fx82 calculators are permitted
Instructions to Invigilators
The examination paper IS TO REMAIN in the examination room
Students are to be provided with 1 script book
Provide extra script books on request
Instructions to Students
The total mark for this paper is 120
Ensure your student number is written on all script books and answer sheets during writing
time
Attempt all questions in all 10 sections, which are of unequal marks value
Answer all questions on the right-hand lined pages of the script book
Start the answer to each question on a new page in the script book
The left-hand unlined pages of script books are for draft working and notes and will not be
marked
State clearly and justify any assumptions made
Write legibly in blue or black pen
Mobile phones, tablets, laptops, and other electronic devices, wallets and purses must be
placed beneath your desk
All electronic devices (including mobile phones and phone alarms) must be switched off
and remain under your desk until you leave the examination venue. No items may be taken to the toilet
INFO20003 Sample Exam
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Section 1 – ER Modelling
The Australian Department of Health and Human Services (DHHS) has a requirement to store the vaccination record of every individual (known as a patient) that resides in Australia who is eligible for a Medicare card. For families, children under the age of 15 are stored on the family card (refer Figure 1). Each Medicare card number is associated with only one family. Every Medicare card has a ‘valid to’ date stored as a month and year on the card (refer Figure 1). Each family member holds a position number on the card. For example to identify Jessica Smith (refer Figure 1) both her Medicare number (1234567890) and position (4) on the Medicare card would be required.
Figure 1: Australian Medicare card (DHHS, Australia)
Each Medicare card is attached to one residential address, contact email, and phone number. For all patients listed on a Medicare card we record their gender, birthdate, first name, last name, and if they have any known allergies (e.g. Penicillin, Cortisone, Codeine). If patients do have an allergy we need to know what the allergy is and the reaction (severe, moderate or mild).
The DHHS needs to record mandatory vaccinations (e.g. Measles, Polio, Whooping Cough, Diphtheria, Tuberculosis and Tetanus) as well as optional vaccination types (e.g. HPV, Flu, Hepatitis A, Hepatitis B, Cholera, Typhoid, Yellow Fever).
For each vaccination event that is given to patients we must record the vaccination type, date of vaccination and the vaccination batch number. Vaccine producers can produce many different types of vaccines and each vaccine can have many batches.
Patients can receive their vaccination from any registered doctor. Every doctor is identified by a unique medical practitioner number (MPN). We record the Medical Practitioner’s title (Dr, Mr, Mrs, Ms, Prof.), first name, last name, registered business address, email, and business phone numbers.
Q1. Draw a conceptual model in either Crow’s Foot or Chen’s notation for this case study (in your script book). Be sure to write down any assumptions you make.
(20 marks)
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INFO20003 Sample Exam Page 4 of 14
Section 2 – SQL-DDL
Figure 2: Data model for SQL DDL
Q2. Write SQL statements to create the tables for the above data model. Be sure to specify primary and foreign keys. You do not need to specify whether the fields are NULL/NOT NULL. Choose appropriate data types for attributes that are not obvious.
(5 Marks)
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Section 3 – SQL-DML
Figure 3 shows the schema for a small business database that contains data about employees, products, customers and orders.
Figure 3: Data model for SQL DML
Write a single SQL statement to correctly answer each of the following questions (3A – 3D). DO NOT USE VIEWS or VARIABLES to answer questions. Query nesting is allowed.
INFO20003 Sample Exam Page 6 of 14
The relations are repeated here for your convenience.
FK employees (empid, lastname, firstname, hiredate, address, phone, managerid)
FK FK
orders (orderid, custid, empid, orderdate, shippeddate, freight, shipname)
customers (custid, companyname, contactname, address, phone)
FK FK
orderdetails (orderid, productid, quantity, discount)
products (productid, productname, unitprice, discontinued)
Q3A. Write a query that returns customers (company names) and the details of their orders (orderid and orderdate), including customers who placed no orders.
(3 marks)
Q3B. Write a query that returns the first name and last name of employees whose manager was hired prior to 01/01/2002.
(4 marks)
Q3C. Write a query that returns customers whose company name is ‘Google’, and for each customer return the total number of orders and total quantities for all products that were not discontinued (‘1’ means discontinued, ‘0’ not discontinued).
(5 marks)
Q3D. Write a query that returns the ID and company name of customers who placed orders in 2007 but not in 2008.
(8 marks)
INFO20003 Sample Exam Page 7 of 14
Section 4 – Query Processing – Joins
Given the schema of Question 3 (SQL-DML), consider the relations Orders and Employees. Imagine that relation Employees has 1,000 pages and relation Orders 50,000 pages. Consider the following SQL statement:
SELECT *
FROM Employees NATURAL JOIN Orders
WHERE freight > 1000;
There are 502 buffer pages available in memory. Both relations are stored as simple heap files. Neither relation has any indexes built on it.
Q4A. What is the cost (in disk I/O’s) of performing this join using the Block-oriented Nested Loops Join algorithm? Provide the formulae you use to calculate your cost estimate.
(3 marks)
Q4B. What is the cost (in disk I/O’s) of performing this join using the Hash Join algorithm? Provide the formulae you use to calculate your cost estimate.
(3 marks)
Q4C. In comparing the cost of different algorithms, we count I/O (page accesses) and ignore all other costs. What is the reason behind this approach?
(2 marks)
Q4D. Which approach should be the least expensive for the given buffer size of 502 pages: 1. Simple Nested Loops Join
2. Page-oriented Nested Loops Join
3. Block-oriented Nested Loops Join
4. Hash Join
Please write the number of the correct response. No need to provide formulae for question 4D.
(2 marks)
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Section 5 – Query Processing – Indexing
Given the schema of Question 3 (SQL-DML), consider the relation OrderDetails. Imagine that the relation OrderDetails consist of 100,000 tuples stored in pages and each page stores 100 tuples. Imagine that the quantity attribute can take any value between 0 and 20 ([0, 20]), and imagine that discount can take any value between 0 and 100 ([0, 100]). Suppose that the following SQL query is executed frequently using this relation:
SELECT *
FROM OrderDetails
WHERE quantity > 15 AND discount > 90;
Your job is to analyse the following query plans and estimate the cost of the best plan utilizing the information given about different indexes in each part.
Q5A. Compute the estimated result size of the query, and the reduction factor of each filter.
(3 marks)
Q5B. Compute the estimated cost of the best plan assuming that a clustered B+ tree index on quantity is (the only index) available. Suppose there are 200 index pages.
(3 marks) Q5C. Compute the estimated cost of the best plan assuming that an unclustered Hash index
on discount is (the only index) available.
(2 marks)
Q5D. If you are given complete freedom to create one index to speed up this query, which index would be the best one to answer this query? Please give complete information about the index, e.g. is it clustered or unclustered, is it hash or B+ tree, which attributes will it cover.
(2 marks)
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Section 6 – Query Optimisation
Given the schema of Question 3 (SQL-DML), consider the relations Employees, Orders and OrderDetails. Imagine that relation Employees has 1,000 pages, relation Orders 5,000 pages, and relation OrderDetails 10,000 pages. Each page stores 100 tuples, and neither relation has any indexes built on it. Consider the following query:
SELECT *
FROM Employees AS E, Orders AS O, OrderDetails AS OD
WHERE E.empid = O.empid AND O.orderid = OD.orderid;
Q6A. Compute the cost of the plan shown below. NLJ is a Page-oriented Nested Loops Join. Assume that empid is the candidate key of Employees, orderid is the candidate key of Orders, and 100 tuples of a resulting join between Employees and Orders can fit on one page.
(4 marks)
Q6B. Would the plan presented below be a valid candidate that System R would consider and compute cost for during query optimisation? Why?
(3 marks)
Q6C. Consider the query presented below. Does the following equivalence class hold? Yes/No and Why?
SELECT firstname, lastname
FROM Employees NATURAL JOIN Orders NATURAL JOIN OrderDetails
WHERE quantity > 5 AND freight < 100
Πfirstname, lastname(σquantity> 5 ٨ freight <100(Employees ↔ σquantity> 5 ٨ freight <100(Πfirstname, lastname(Employees
Orders Orders
OrderDetails)) OrderDetails))
(3 marks)
INFO20003 Sample Exam
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Section 7 – Normalisation
Q7. The table shown below is part of an office inventory database. Identify the design problems and write a revised table structure in 3rd Normal Form (3NF) that corrects those problems. For each step explicitly identify which normal form is violated and briefly explain why.
Write the normalised tables in a textual format, as in:
FK TableName (PrimaryKey, Column, ForeignKey)
AnotherTable (PrimaryKey, Column, AnotherColumn)
Item ID is the candidate key for this table. Item ID determines Description, Quan, Cost/Unit and Dept, while Dept determines Dept Name and Dept Head.
Item ID
Description
Dept
Dept Name
Dept Head
Quan
Cost/Unit
Inventory Value
4011 5 ft desk
4020 File cabinet 4005 Executive chair 4036 5 ft desk
Section 8 – Data Warehousing
200 1000 75 750 100 500 200 1400
(10 marks)
MK Marketing
MK Marketing
MK Marketing
ENG Engineering Ahmad Rashere 7
Jane Thompson 5 Jane Thompson 10 Jane Thompson 5
You are making a data warehouse for a real estate agency. The company wants to track information about the selling of their properties. Whenever a buyer comes into the office an agent takes that person to a number of properties and deals with the buyer. This warehouse keeps information about the agents (real estate license#, first name, last name, phone #, and branch office), buyers that come in (buyer id, first name, last name, phone #, max price), and property (property#, property address, number of rooms, pool, owner id). The information managers want to be able to find is the number of times a property is viewed, sales price and commission. Sales commission is additional compensation the agent receives for exceeding expectations. The information needs to be accessible by agent, by buyer, by property and for different time (day, week, month, quarter and year).
Q8A. Draw a star schema to support the design of this data warehouse, showing the attributes in each table. Use PK to denote primary key, PFK to denote primary foreign key, and FK to denote foreign key. You do not need to specify data types nor whether the fields are NULL/NOT NULL.
(8 marks)
Q8B. Why are star schemas preferred over relational database designs to support decision making?
(2 marks)
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Section 9 – NoSQL and Database Administration
Q9A. There are trade-offs between the principles of ACID and BASE. Discuss the trade-off between availability and consistency for relational and NoSQL databases. Illustrate your answer using either the example of Facebook or the example of Twitter.
(5 marks)
Q9B. Vine is a social media sharing service where users can host 6-second video clips within multiple categories (e.g. “Comedy”, “Science”, “Social”). Part of the database schema for the Vine service is given below.
There are 15 different categories that users can share videos about and 1 million users to start with. A user posts 5 videos on average per month. Assume that the average storage requirement for the BLOB data type is 20,000 bytes.
Estimate the disk space requirements only for the Video table at go-live and after one month of operation.
(5 marks)
Storage requirements for different data types
Data type
Storage requirement (bytes)
INT
4
BLOB
65,535 (Max)
DATETIME
8
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Section 10 – Multiple Choice Questions
There are fifteen multiple choice questions. Each question is worth 1 mark. There is only one correct answer per question. Write the question number and your answer in the script book.
Q10A. Which of the following is NOT part of the database development lifecycle? A) Implementation
B) Maintenance
C) Requirement analysis
D) First-level support
Q10B. A relation which is NOT in the conceptual and logical models but is made available to users is a:
A) Datatype B) View
C) Revoke D) Grant
Q10C. Which of the following is NOT a valid join? A) Sort-merge
B) Hash
C) Nested loop
D) Heap
Q10D. Which of the following is NOT a true statement about data and information?
A) Dates and audio are two examples of data
B) Informationhasbeenprocessedsothatitincreasestheaudience’sknowledge C) Information is used to create data
D) The term “data” refers to raw facts
Q10E. Which of the following is NOT true about normal forms?
A) A table in 1NF must have no multivalued attributes
B) A table in 2NF must have no multivalued attributes
C) A table in 2NF must have no transitive functional dependencies D) A table in 3NF must have no transitive functional dependencies
Q10F. Which of the following is NOT one of the basic operations of Relational Algebra? A) Set-difference
B) Cross-product
C) Equality
D) Union
Q10G. The structure of a Clustered B+ tree Index does NOT contain: A) Datapages
B) Leaf nodes
C) Internal nodes
D) Root node
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Q10H. Which of the following is NOT a true statement about projection?
A) Projection can be accomplished by hashing
B) The cost of projection by external merge sort depends on the reduction factor
C) Projection algorithms are designed to remove duplicates from the result set
D) Projection by external merge sort uses the same sorting approach as sort-merge join
Q10I. Which of the following is NOT a commonly-used level of lock granularity? A) Field-levellocking
B) Row-levellocking
C) Table-level locking
D) Database-level locking
Q10J. Which of the following is NOT a valid type of logical database backup? A) Incrementalbackup
B) Onlinebackup
C) Onsite backup
D) Offline backup
Q10K. Which of the following is NOT a normalization concept?
A) B) C) D)
Q10L. A) B) C) D)
Q10M. A)
B) C) D)
Non-keydependency Partialfunctionaldependency Candidate key
Determinants
Which of the following is NOT a file organisation type? Hash file organisation
Index file organisation
Heap file organisation
Sorted file organisation
Which of the following is NOT an SQL command category? DDL
DML
DCL
DSL
Q10N. Which of the following is NOT a part of query optimisation? A) Planenumeration
B) Costing
C) Building a new index
D) Result size estimation
Q10O. Which of the following is NOT true about choosing data types?
A) May help improve query optimisation
B) Help DBMS store and use information efficiently
C) Help minimise storage space
D) May help improve data integrity
END OF THE EXAM
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