Fall 2012
CS 370 / IT 376 Exam 2
Page 1
Database Management Systems
11/2//12
Name_________Key______________
1. True/False.
[20 pts]
__T___ A null value has multiple interpretations and is one purpose for first normal form.
__ T___ A view is an acceptable way to offer simpler, unnormalized tables to the user.
__F___ DELETE-ing from a view that is based on a simple natural join of its base tables is acceptable.
__T ___ A view can provide an implementation of virtual attributes.
__T __ In an object database, the objects in object storage are persistent in secondary storage.
__T ___ In an object database, an object is related to a set of other objects through explicit relationship
clauses.
__F __ 3NF relations allow transitive dependencies.
__T___ Cardinality in an ER or UML diagram can specify lower and upper limits to numbers of
participants in a relationship.
__T ___ NOT NULL UNIQUE tags on an attribute implies the attribute is a candidate key.
__F ___ JDBC uses a statement level interface and access protocol for embedded SQL in Java.
__T __ A cursor provides access to exactly one tuple at a time within result set.
__T ___ The SQLSTATE system variable holds a 5 digit error or success code string of the last SQL
operation.
__T ___ The UML diagram rectangles essentially represent entities, while relationships are lines.
__T ___ Object oriented databases easily implement inheritance.
__T ___ Functional dependency analysis is at the center of the normalization of a relational table.
__T __ Normalization attempts to reduce or eliminate redundant facts stored in a database table.
__T __ Decomposition of a table for normalization results in two or more tables to replace the original
table.
__T ___ A normalization goal is a loss-less join decomposition.
__F__ The SQL SELECT statements specifies the sequence of operations the server uses to answer the
query.
__T ___ Triggers provide a mechanism to monitor specific changes to a table and take perform additional
actions based on the altered data.
Fall 2012
CS 370 / IT 376 Exam 2
Page 2
2. Normalize the relation below by appropriate decomposition. Underline the primary key
attributes of each table. Language is a multivalued attribute.
Books (ISBN, Title, CopyrightYear, LeadAuthor, Publisher, PublisherURL, AuthorEmail,
Language)
[15 pts]
Books( ISBN, Title, CopyrightYear, LeadAuthor, Publisher)
Authors(LeadAuthor, AuthorEmail)
Publishers(Publisher, PublisherURL)
Languages(ISBN, Language) // actually the different languages would likely require different ISBNs,
but because it’s specified as a multivalued attribute, this is the implementation.
3. Explain what the following SQL trigger accomplishes. Any syntax errors are not intended and
there may be some liberties taken with the grammar.
[10 pts]
CREATE TRIGGER WatchIt
AFTER UPDATE (balance) OR INSERT
ON accounts
FOR STATEMENT
(UPDATE accounts
SET lastChanged = Now
WHERE acctNo = NEW.acctNo;
INSERT INTO accountsLog
VALUES (NEW.acctNo, NEW.balance, OLD.balance, Now, Username);
);
When the ‘balance’ attribute of the ‘accounts’ table is updated or a new tuple is inserted, the
‘lastChanged’ attribute is updated with a timestamp, offloading the need for timestamp
acquisition by the application.
Further the account information of the old and new balances, along with a timestamp and
username of the application was logged. This is again behind the scenes and not in control by
the applications or even SQL statements.
Fall 2012
CS 370 / IT 376 Exam 2
Page 3
4. Below is a JDBC application (which should look vaguely familiar). Give short answers the
questions below referring to this application, or fill in the blanks as directed.
[20 pts]
import java.io.*;
import java.sql.*;
public class dbdemo {
public static void main (String[] args) throws IOException{
String connString;
String input;
int population,votes;
String stateName;
BufferedReader br = new BufferedReader( new InputStreamReader(System.in));
Connection conn = null;
Statement stmt = null;
ResultSet res = null;
PreparedStatement ps =
,P.STATE is inserted (b)
null;
String query = "SELECT P.PRES FROM PRESIDENTS P";
String pQuery = "SELECT * FROM STATES WHERE POP BETWEEN ? AND ?";
connString = "jdbc:postgresql://itcsserver/pres?user=guest&password=guest ";
try {
Class.forName("org.postgresql.Driver");
conn = DriverManager.getConnection(connectionString ); //****A****
stmt = conn.createStatement();
res = stmt1.executeQuery(query);
while (res.next()){
Add
System.out.println(res.getString("PRES"));
}
ps = conn.prepareStatement(__pQuery___);
System.out.print("Enter low population level: ");
input = br.readLine();
ps.setInt(____1___, Integer.parseInt(input));
System.out.print("Enter high population level: ");
input = br.readLine();
ps._setInt_( 2, Integer.parseInt(input));
a similar line for “STATE” (b)
res = ps.executeQuery();
//****B****
while(res.next()){
stateName = res.getString("STATE");
population = res.getInt("POP");
//****C****
votes = res.getInt("STATES_VOTES");
System.out.println(stateName + " has population "+population
+" and holds "+votes+" electoral votes");
}
} catch (Exception e) {
System.out.println(e.toString());
}
System.exit(0);
}
}
a. We want to access a database on a SQL Server instead. What two lines must changed? Circle
the parts of the lines and indicate what needs to be changed. [4]
Square blue boxes above show where postgres would be replaced with SqlServer versions
Fall 2012
CS 370 / IT 376 Exam 2
Page 4
b. Show the modifications in the first retrieval that are necessary to retrieve and display the
president’s home state with the president’s name. Make all the edits clear! [5]
See text boxes above marked (b)
c. There are three blanks in the code above. Fill them in to make the prepared statement retrieval
work. [3]
See filled in blanks.
d. Describe two problems that could arise at the point of the database connection (Statement
labeled “A”). [4]
Server doesn’t exist or cannot be reached. Database doesn’t exist. Username and/or password
bad. User not permitted access.
e. Describe a viable exception that can be thrown at the statements labeled “B” and ”C”. [4]
B. Syntax of query flawed, table and/or attributes referenced do not exist
C. Returned attribute value of ‘pop’ is not integer
For the SQL queries use the following relational schema for a rental company database. Keys are
(mostly) underlined. The attributes should be self-evident. If not, please ask for clarification.
Customers may rent several items at a time and they are all listed under one invoice. Payment is
due upon return of the items. Credit cards are used in lieu of a deposit and the hold is released on
return of the items, but payment can be by check as well.
CUSTOMER(custID, name, address, zip, phone, custType)
CSZ(zip, city, state)
INVOICE(invID, custID, dateOfInv, finalTotalBill, crCardNo)
ITEMSONHAND(typeID, description, totalOwned, dailyRentRate)
ITEMDESCR(itemID, typeID, condition, dateBought, purchasePrice)
RENTED(invID, itemID, dateReturned) – (dateReturned is null if still rented)
PAYMENT(invID, pmtThhype, crCardOrCheckNo, amount, date)
[35 pts]
Quick syntax for SQL, where [] means optional, {op1|op2|...} means choice
SELECT [DISTINCT] {* | attribute-list | aggregate functions}...
FROM table {, table | NATURAL JOIN table | LEFT OUTER JOIN table {USING(attr) | ON condition}}*
WHERE condition
[GROUP BY attr [HAVING condition]]
SQL conditions consist of <,>,<=,>=, <>,=, AND, OR, BETWEEN value AND value
[NOT] EXISTS ({list | SELECT...}),
rel-op {ANY|SOME|ALL} ({ list | SELECT...}), IS [NOT] NULL
Aggregate functions: COUNT(*|[DISTINCT] attr), MIN(attr), MAX(attr), SUM(attr), AVG(attr)
Fall 2012
CS 370 / IT 376 Exam 2
Page 5
a) List all names and phone numbers of ‘contractor’ customer type. [5]
SELECT C.name, C.phone
FROM CUSTOMER C
WHERE C.custType=’contractor’
b) List names of customers from zip 16652 who have had single invoices of at least $500. [6]
SELECT C.name, I.finalTotalBill
FROM CUSTOMER C Natural Join INVOICE I
WHERE C.zip=’16652’ AND I.finalTotalBill >=500
c) The large barbeque roasters (typeId=BBQRSTR) bought before 2005 were discovered to
contain asbestos. List names and phone numbers of customers who have ever rented one of
these items. [6]
SELECT C.name, C.phone
FROM CUSTOMER C Natural Join INVOICE I Natural Join RENTED R
Natural Join ITEMDESC D
WHERE D.typeId=’BBQRSTR’ AND D.dateBought<’2005-01-01’
d) List customer names who have not rented anything since Jan 1 2010. [6]
SELECT C.name
FROM CUSTOMER C
WHERE NOT EXISTS ( SELECT I.custId
FROM INVOICE I
WHERE I.dateOfInv >=’2010-01-01’
AND C.custId=I.custId)
e) List each customer by name and phone number and their total invoice value. [6]
SELECT C.Name, C.phone, SUM(I.finalTotalBill)
FROM CUSTOMER C Natural Join INVOICE I
GROUP BY C.custId
f) List customer names from Pennsylvania (‘PA’) who have at least one item not returned but
list the number of unreturned items. [6]
SELECT C.name, C.phone, COUNT(R.itemID)
FROM CUSTOMER C Natural Join INVOICE I Natural Join RENTED R
Natural Join CSZ Z
WHERE Z.state = ‘PA’ and R.dateReturned is null
GROUP BY C.custID