Fall 2011 CS 370 / IT 376 Exam 2 Page 1Database Management Systems

11/4/11Name__________Key_____________

1. True/False.[17 pts]

______ Disk accesses are only a thousand times slower than RAM access.

______ A cylinder on a disk is the set of spiraled tracks found on one surface of a disk platter.

______ A heap or pile file maintains the data in sorted order by primary key.

______ In an object database, the objects in object storage are persistent in secondary storage.

______ In an object database, an object is related to a set of other objects through explicit relationship clauses.

______ The UML diagram blocks essentially represent entities, while relationships are lines.

______ Object oriented databases implement inheritance.

______ 3NF relations allow no transitive dependencies.

______ Null values have multiple interpretations and is one reason for first normal form.

______ A view is an acceptable way to present unnormalized tables to the user.

______ DELETE-ing from a view that is based on a row selection of a base tables is acceptable.

______ A view can provide an implementation of virtual attributes.

______ Cardinality in an ER diagram can specify lower and upper limits to numbers of participants in a relationship.

______ NOT NULL UNIQUE tags on an attribute implies a foreign key.

______ JDBC uses a statement level interface and access protocol for embedded SQL in Java.

______ A cursor provides access to exactly one tuple at a time within result set.

______ The SQLSTATE system variable holds a Unix based integer error or success code.

2. Disk drives.a. If a disk has sectors that are 2048 bytes and tuple sizes are 40 bytes, describe how the data in a

large relational table of those tuples would likely be placed in those sectors. Do not split a tuple across a sector.

[4 pts]

b. A disk spins at 7200 rpm (revolutions per minute) and average read/write heads armature motion is 10 ms. (ms = 1/1000 sec)

[8 pts]Average seek time = ___________ms, and average rotational latency = ______________ms.

If there are 100 sectors per track, the transfer time for 5 contiguous sectors = _____________ms.

The total expected access time for these 5 sectors is ___________________ms.

Fall 2011 CS 370 / IT 376 Exam 2 Page 23. 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.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 = 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); //****B****while (res.next()){ System.out.println(res.getString("PRES"));

}ps = conn.prepareStatement(_____________);

System.out.print("Enter low population level: "); input = br.readLine();

ps.setInt(______, Integer.parseInt(input)); //****C**** System.out.print("Enter high population level: "); input = br.readLine();

ps.setInt(______, Integer.parseInt(input));

res = ps.executeQuery();while(res.next()){ stateName = res.getString("STATE"); population = res.getInt("POP"); //****D**** 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); }}

[30 pts]a. We want to access an Oracle database instead. What has to be changed? [4]

org.postgresql.Driver replaced by one from Oracle and the connections string protocol will be changed

b. Show the modifications in the first retrieval that are necessary to display the president’s political party with the president’s name. Make the edits clear! [6]

Fall 2011 CS 370 / IT 376 Exam 2 Page 3c. There are three blanks in the code above. Fill them in to make the prepared statement retrieval

work. [6]

d. Describe 2 purposes are served by a database connection. (don’t use the word connection in your answer!) [6]

establish communication to the server, choose database on serverauthorize as user

e. Describe an exception that can be thrown at the statements labeled “A”, “B”,”C” and “D”. [8]

A. bad URL, db not exist, not authorized

B. malformed query, table/attribute names wrong, not authorized

C. input is malformed, reference to ? is out of range

D. Data not integer/numeric or field name non-existent

4. Explain what the following SQL trigger accomplishes. Any syntax errors are not intended and there are some extensions to the grammar.

[9 pts]CREATE TRIGGER StateStatsUpdate1 AFTER UPDATE (pop) OR DELETE OR INSERT ON states FOR STATEMENT (UPDATE state_stats SET value = (SELECT Sum(pop) FROM states) WHERE attribute = 'totalPop'; UPDATE state_stats SET value = (SELECT Count(*) FROM states) WHERE attribute = ‘stateCount’; );

When any modification happens to the state the trigger runs and updates the states_stats table with current population level and number of states in the tables

Fall 2011 CS 370 / IT 376 Exam 2 Page 4For the SQL queries use the following relational schema for a volunteer organization that needs to keep

track of members, projects, and sponsors, and the relationships between them. Each member is given a memberID. Each project has a unique name, and has a coordinator, a budget, a timeframe, and so on. A sponsor may be a business, foundation, government agency, and other source that donates money for projects. Every project must have at least one sponsor, but may have several. Projects are worked on by the members of the organization. Members may work on several projects. Assume sponsor names and project names are unique, but member names may not be.

Members (memId, name, street, zip, phone, dateJoined)CorpSponsors (cName, street, zip, phone, type, contactMemId)Projects (pName, coordMemId, budget, startDate, endDate)ProjectSponsors (pName, cName, amountDonated, dateDonated)ProjectWorkers (pName, memId, numberHoursTotal)CSZ (zip, city, state)

[6 pts each=36]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)

a) List all members from the 16652 zip area.

SELECT * FROM Members mWHERE m.zip = 16652;

b) List member names and phone numbers who have worked at least 10 hours on the ‘HuntingdonHH’ project.

SELECT m.name, m.phoneFROM Members m NATURAL JOIN ProjectWorkers pwWHERE pw.numberHoursTotal>=10AND pw.pName=’HuntingdonHH’

Fall 2011 CS 370 / IT 376 Exam 2 Page 5c) For projects that are still ongoing (endDate is later than today, use now()), what are the

project sponsor corporations and contact person names? (Hint: natural joins don’t work completely across all joins)

SELECT p.pName, cs.cName, m.nameFROM Projects p NATURAL JOIN ProjectSponsors ps NATURAL JOIN CorpSponsors cs , Members mWHERE p.endDate > now()AND m.memID = cs.contactMemID

d) What projects have had more than $50000 in total donations? (Hint: group by…)

SELECT p.pName, SUM(p.amountDonated)FROM ProjectSponsors pGROUP BY p.cNameHAVING SUM(p.amountDonated)>50000

e) What projects have no corporate sponsors? (Hint: use outer join or except)

SELECT p.pNameFROM Projects p LEFT OUTER JOIN ProjectSponsors psWHERE ps.cName is null

(SELECT p.pNameFROM Projects p)EXCEPT (SELECT s.pNameFROM ProjectSponsors s)

f) How many different cities are represented by the corporate sponsors? (Hint: use aggregate Count(Distinct attribute))

SELECT Count(Distinct z.city)FROM CorpSponsors c NATURAL JOIN CSZ z