Web-Database Integration
Week 7
LBSC 690
Information Technology
Agenda
•	Questions

•	E-R Modeling

•	PHP

•	Mythical person-month

•	Midterm review
Key Ideas
•	Databases are a good choice when you have
–	Lots of data
–	A problem that contains inherent relationships

•	Design before you implement
–	This is just another type of programming
–	The mythical person-month applies!

•	Join is the most important concept
–	Project and restrict just remove undesired stuff
Getting Started with E-R Modeling
•	What questions must you answer?

•	What data is needed to generate the answers?
–	Entities
•	Attributes of those entities
–	Relationships
•	Nature of those relationships

•	How will the user interact with the system?
–	Relating the question to the available data
–	Expressing the answer in a useful form
“Project Team” E-R Example
Components of E-R Diagrams
•	Entities
–	Types 
•	Subtypes (disjoint / overlapping)
–	Attributes
•	Mandatory / optional
–	Identifier
•	Relationships
–	Cardinality
–	Existence
–	Degree
Making Tables from E-R Diagrams
•	Pick a primary key for each entity
•	Build the tables
–	One per entity
–	Plus one per M:M relationship
–	Choose terse but memorable table and field names
•	Check for parsimonious representation
–	Relational “normalization”
–	Redundant storage of computable values
•	Implement using a DBMS

•	1NF: Single-valued indivisible (atomic) attributes
–	Split “Doug Oard” to two attributes as (“Doug”, “Oard”)
–	Model M:M implement-role relationship with a table

•	2NF: Attributes depend on complete primary key
–	(id, impl-role, name)->(id, name)+(id, impl-role)

•	3NF: Attributes depend directly on primary key
–	(id, addr, city, state, zip)->(id, addr, zip)+(zip, city, state)

•	4NF: Divide independent M:M tables
–	(id, role, courses) -> (id, role) + (id, courses)

•	5NF: Don’t enumerate derivable combinations
Normalized Table Structure
•	Persons: id, fname, lname, userid, password
•	Contacts: id, ctype, cstring
•	Ctlabels: ctype, string
•	Students: id, team, mrole
•	Iroles: id, irole
•	Rlabels: role, string
•	Projects: team, client, pstring
Ways of Generating Web Pages
•	Static: Written in a markup language
–	HTML, XML

•	Dynamic: Generated using a program
–	Common Gateway Interface [Perl] (.cgi)
–	Java servlets

•	Dynamic: Generated from a database
–	Cold Fusion (.cfm)
–	PHP (.php)
Why Database-Generated Pages?
•	Remote access to a database 
–	Client does not need the database software

•	Serve rapidly changing information
–	e.g., Airline reservation systems

•	Provide multiple “access points”
–	By subject, by date, by author, …

•	Record user responses in the database
Issues to Consider
•	Benefits
–	Multiple views
–	Data reuse
–	Scalable
–	Access control

•	Costs
–	Formal modeling
–	Complex (learn, design, implement, debug)
–	Brittle (relies on multiple communicating servers)
–	Not crawlable
Downside
•	Brittle
–	Depends on multiple servers

•	Complex
–	Learning, design, implementation, debugging

•	Formally modeled

Three Ways to Serve Data
Microsoft “Data Access Pages”
•	Displays database content on Web pages
–	Not very useful for changing database content

•	Drag-and-drop design in Microsoft Access
–	“Reports” are designed for printing
–	“Pages” are designed for the Web

•	Requirements:
–	Microsoft Web Server (not Apache)
–	IE 5 or higher Web browser (not Firefox)
–	“Office Web Components” on client machine
•	IE 7 fails gracelessly without them!
Data Access Page Example

PHP Programming Environments
•	You need three systems on the same server:
–	PHP (programming language)
–	MySQL (DBMS)
–	Apache (Web server)

•	WampServer (for PC)
–	Includes GUI tools

•	OTAL (Sun Unix) supports Web deployment
–	Requires a text editor (e.g., emacs) or FTP
Making PHP
----- HTML stuff -----
<?php
	----- PHP stuff -----
?>
----- HTML stuff -----

http://---URL stuff---/xxxxx.php
WampServer
•	Download and install
–	From http://www.en.wampserver.com/

•	Make sure the server is working
–	Point a Web browser at http://localhost/
–	Select phpinfo.php
•	Error reporting on?  MySQL listed?

•	Test the connection to MySQL
–	Run mysql_test.php (“Resource id #2” indicates ok)
      <?php
          echo mysql_connect(�elocalhost�f, �eroot�f, �e�f);
      ?>
Connecting PHP to MySQL
•	On WAMP:
$dbc=mysql_connect (‘localhost’, ‘userid’, ‘password’);

•	On OTAL:
$dbc=mysql_connect(‘:/export/software/otal/mysql/run/mysqld.sock’,
				‘userid’, ‘password’);
Create a MySQL Database
•	“root” user creates database + grants permissions
–	Using the WAMP console (or mysql –u root –p)
•	root has no initial password; just hit <enter> when asked
–	By the system administrator on OTAL (otal.umd.edu)
      CREATE DATABASE project;
      GRANT SELECT, INSERT, UPDATE, DELETE, INDEX, ALTER, CREATE, DROP ON project.* TO ‘foo’@’localhost’ IDENTIFIED BY ‘bar’;
      FLUSH PRIVILEGES;
•	Start mysql
–	MySQL console for WAMP, ssh for OTAL
                                                                                         mysql –u foo –p bar
•	Connect to your database
      USE project;
Creating Tables
CREATE TABLE contacts (
  ckey	MEDIUMINT UNSIGNED NOT NULL AUTO_INCREMENT,
  id		MEDIUMINT UNSIGNED NOT NULL,
  ctype	SMALLINT UNSIGNED NOT NULL,
  cstring	VARCHAR(40) NOT NULL,
  FOREIGN KEY (id) REFERENCES persons(id) ON DELETE CASCADE,
  FOREIGN KEY (ctype) REFERENCES ctlabels(ctype) ON DELETE RESTRICT,
  PRIMARY KEY (ckey)
) ENGINE=INNODB;

•	To delete: DROP TABLE contacts;
Populating Tables
INSERT INTO ctlabels
  (string) VALUES
  ('primary email'),
  ('alternate email'),
  ('home phone'),
  ('cell phone'),
  ('work phone'),
  ('AOL IM'),
  ('Yahoo Chat'),
  ('MSN Messenger'),
  (‘other’);

•	To empty a table: DELETE FROM ctlabels;
“Looking Around” in MySQL
•	SHOW DATABASES;

•	SHOW TABLES;

•	DESCRIBE tablename;

•	SELECT * FROM tablename;

Structured Query Language
DESCRIBE Flight;
Structured Query Language
SELECT * FROM Flight;
Structured Query Language
SELECT Company.CompanyName, Company.CompanyPhone, Flight.Origin, Flight.DepartureTime 
FROM Flight,Company
WHERE Flight.CompanyName=Company.CompanyName
   AND Flight.AvailableSeats>3;
Statements in PHP
•	Sequential
{…; …;…;}
Semicolons are required at the end of every statement
•	Conditional
if (3==i) {…} else {…}
•	Loop 
for ($i=0; $i<10; $i++) {…}
while ($row=mysql_fetch_array(…)) {…}
foreach ($array as $key => $value) {…} 
•	Braces are optional around a single statement
Variables
•	Name starts with a $
–	Case sensitive (assume everything could be!)

•	Hold a value
–	Number (integer, float)
–	String (double quotes, \ escape character)
–	TRUE, FLASE
–	NULL

•	Need not be declared (automatically “cast”)
Operators in PHP
•	Arithmetic operators
+  -  *  / 

•	Logical operators
<  <=  ==  !=  >=  >  &&  ||  !

•	String operator
.
Arrays in PHP
•	A set of key-element pairs
$days = array(“Jan”->31, “Feb”=>28, …);
$months = explode(“/”, “Jan/Feb/Mar/…/Dec”);
$_POST

•	Each element is accessed by the key
–	{$days[“Jan”]}
–	$months[0];
Functions in PHP
•	Declaration
function multiply($a, $b=3){return $a*$b;}

•	Invoking a method
$b = multiply($b, 7);

•	All variables in a function have only local scope
•	Unless declared as global in the function

Using PHP with (X)HTML Forms
<form action=“formResponseDemo.php”, method=“post”>
	email: <input type=“text”, name=“email”, value=“<?php echo $email ?>”, size=30 />
	<input type=“radio”, name=“sure”, value=“yes” /> Yes
	<input type=“radio”, name=“sure”, value=“no” /> No
	<input type=“submit”, name=“submit”, value=“Submit” />
	<input type=“hidden”, name=“submitted”, value=“TRUE” />
</form>

if (isset($_POST[“submitted”])) {
	echo “Your email address is $email.”;
} else {
	echo “Error: page reached without proper form submission!”;
}

Ajax Applications
•	Google Maps
–	http://maps.google.com
•	Google Suggest
–	http://www.google.com/webhp?complete=1&hl=en
•	Sajax Tables
–	http://labs.revision10.com/?p=5
•	Sajax
–	http://www.modernmethod.com/sajax/
 Discussion Point: 
Mythical Person-Month
•	Why is software development different from manufacturing car?

•	If it would take one person three months, why does it take four people SIX months?
Trading People and Months is Hard
•	Sequential constraints

•	Communication

•	Training
Estimating Completion Time
•	Rules of thumb
–	1/3 specification
–	1/6 coding
–	1/2 test planning, testing, and fixing!

•	Add time for coding to learn as you go, but don’t take time away from the other parts!
–	Reread the section on “gutless estimating” if you are tempted
The Grand Plan
The Midterm
•	1 hour and 15 minutes
–	Second half of class: project team meetings

•	Quiz/homework should be good preparation
–	A variety of question types
–	Some questions will require computer use

•	Lots of prior exams are available
–	Some have solutions available

•	Open book/notes/Internet/mind/…
–	Just don’t get help from another person
Computer Systems
•	Hardware 
–	Types of hardware
–	Storage hierarchy
–	Moore’s law
•	Software
–	Types of software
–	Types of interfaces
Networks
•	Types of Networks
–	LAN, WAN, Internet, Wireless
•	Packet Switching
–	Ethernet, routers, routing tables
•	Layered Architecture and protocols
–	TCP/UDP
–	IP address/domain name
Structured Documents
Multimedia
Programming
•	Programming languages
–	Machines require specific instructions
–	Humans require high-level abstraction

•	Control structures
–	Sequential execution
–	Conditional
–	Iteration

•	Javascript
Databases
•	Structured information
–	Field->record->table->database
–	Primary key
•	Normalized tables (relations)
–	Remove redundancy, inconsistency, error
–	Easy update, search
•	Join links tables together
–	Through foreign key
•	Access provides visual operations
Web-Database Integration
•	Microsoft “Data Access Pages”

•	Server-side database integration

•	Ajax

•	Mythical person-month