Lecture 11 Introduction to Relational Database

Lecture 11Introduction to Relational Database

Presented ByDr. Shazzad Hosain

Asst. Prof. EECS, NSU

CSC382: Internet & Web TechnologyMySQL Database System

Lecture Contents Database Concepts SQL Commands Database Connectivity

Connectivity Example DDL Query DML Query MySql Functions

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Client-Server Interaction

MySQLServer

ClientProgram

Make a request(SQL query)

Get results

Client program can be a MySQL command line client, GUI client, or a program written in any language such as C, Perl, PHP, Java that has an interface to the MySQL server.

MySQL databases are ideal for storing that data we have collected about a user or for holding user preferences between visits. It is free and it is easy.

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3-Tier Architecture

WebBrowser(Client)

DatabaseServer

WebServer PHP

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Database Management System• Collection of data =

Database (DB)• Set of interrelated

data and programs to access those data is called DBMS

• DBMS Provides environment that is convenient and efficient to use for data retrieval and storage

Data Data Data

Program Program

ProgramProgram

Database

DBMS

Relational Database Basics• Today’s database implementations are almost all based on the

relational model• A relational database management system consists of a number of

databases.• Each database consists of a number of tables.• It represents data in a two-dimensional table called a relation• The attributes are located across the top of the relation

attributesname

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Tuples• The rows in the relation (other than attribute row) are called tuples• A tuple has one component or value for each attribute of the relation• A tuple should never appear more than once in a relation• We must ensure that the relation has a sufficient set of attributes so

that no two tuples will have the same values for all attributes

tuples

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Database Languages (Query) DBMS provide two types of language

– One to specify schema and create the database– One to express database queries and updates

1. Data-Definition Language (DDL Query)– Schema is specified by a set of definitions expressed by the DDL– Result is set of tables stored in the Data Dictionary– Data Dictionary is a file that contains metadata, data about data

2. Data-Manipulation Language (DML Query)– Language for accessing and manipulating the data organized by

the appropriate data model. That is, data retrieval, insertion, deletion, modification

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SQL commands SHOW, USE

• SHOW– Display databases or tables in current database;– Example (command line client):– show databases;– show tables;

• USE– Specify which database to use– Example– use bookstore;

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Entering commands (1)

• Show all the databases– SHOW DATABASES;mysql> SHOW DATABASES;+-------------+| Database |+-------------+| bookstore || employee_db || mysql || student_db || test || web_db |+-------------+

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Entering commands (2)

• Choosing a database and showing its tables– USE test;SHOW tables;mysql> USE test;Database changedmysql> SHOW tables;+----------------+| Tables_in_test |+----------------+| books || name2 || names || test |+----------------+4 rows in set (0.00 sec)mysql>

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Entering commands (3)

• Show the structure of a table– DESCRIBE names;

mysql> DESCRIBE names;+-----------+-------------+------+-----+---------+----------------+| Field | Type | Null | Key | Default | Extra |+-----------+-------------+------+-----+---------+----------------+| id | int(11) | | PRI | NULL | auto_increment || firstName | varchar(20) | | | | || lastName | varchar(20) | | | | |+-----------+-------------+------+-----+---------+----------------+3 rows in set (0.00 sec)

mysql>

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SQL Commands• SQL is a reasonably powerful query language.

• However it is incredibly simple. You can learn it in a night.

• The fundamental SQL commands are:

– CREATE– SELECT– INSERT– DELETE– UPDATE

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Example of SQL DDL

studentID first_name

USE test;CREATE TABLE marks ( studentID SMALLINT AUTO_INCREMENT NOT NULL, first_name VARCHAR(20) NOT NULL, last_name VARCHAR(20) NOT NULL, mark SMALLINT DEFAULT 0 NOT NULL, PRIMARY KEY (studentID));

markstable

last_name mark

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marks.sql

-- Insert some rows into marks tableINSERT INTO marks (first_name, last_name, mark) VALUES ('Fred', 'Jones', 78);INSERT INTO marks (first_name, last_name, mark) VALUES ('Bill', 'James', 67);INSERT INTO marks (first_name, last_name, mark) VALUES ('Carol', 'Smith', 82);INSERT INTO marks (first_name, last_name, mark) VALUES ('Bob', 'Duncan', 60);INSERT INTO marks (first_name, last_name, mark) VALUES ('Joan', 'Davis', 86);

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Conditional Creation

• Conditional database creation– CREATE DATABASE IF NOT EXISTS db_name;

• Conditional table creation– CREATE TABLE IF NOT EXISTS table_name;

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• Selecting the complete tableSELECT * FROM marks;

+-----------+------------+-----------+------+| studentID | first_name | last_name | mark |+-----------+------------+-----------+------+| 1 | Fred | Jones | 78 || 2 | Bill | James | 67 || 3 | Carol | Smith | 82 || 4 | Bob | Duncan | 60 || 5 | Joan | Davis | 86 |+-----------+------------+-----------+------+5 rows in set (0.00 sec)

Entering commands

PHP to MySQL Connectivity• mysql_connect() establishes a connection to a MySQL

server. • It takes 3 parameters.

– The address of the server– Your Username for that db account– Your password

$conn = mysql_connect(“address",“user“,“pass”);

• XAMPP mysql server is found at the following address: localhost

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• In our code mysql_select_db() then tells PHP that any queries we make are against the mydb database.

mysql_select_db(“dbname",$conn);• We could create multiple connections to

databases on different servers. But for now, you’ll only need one database.

• mysql_query() does all the hard work.• Using the database connection identifier, it sends a line

of SQL to the MySQL server to be processed. • This is the key command for interacting with the

database.

PHP to MySQL Connectivity

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Extracting Query Result

• Finally, mysql_result() is used to display the values of fields from our query:

mysql_result($result,0,"first");

• Using $result, we go to the first row, which is numbered 0, and return the value of the specified fields.

• Close the connection to the database server mysql_close();

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First MySql/PHP Program<?$db = mysql_connect("localhost", "root"); mysql_select_db("mydb",$db);$result = mysql_query("SELECT * FROM

employees");

$firstname = mysql_result($result,0,"first");$lastname = mysql_result($result,0,“last");$address = mysql_result($result,0,“address");

?>

Hello <?=$firstname?> <?=$lastname?> <BR>Your address is <?=$address?>

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Unpolitically Correct Create Example

• For example, to create a table from our PHP code you might type:

mysql_query(“CREATE TABLE players ( name varchar(30),

age integer)”);

• Remember that this is something that you would only want to do once – once the table is created we don’t want to wipe it by accident

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MySQL Insert Example• Equally we can populate our tables with INSERT statements via

mysql_query()

mysql_query(“INSERT INTO player VALUES (‘Zidane',32)”);

mysql_query(“INSERT INTO player VALUES (‘Ronaldinho',28)”);

mysql_query(“INSERT INTO player VALUES (‘Pele',58)”);

• These are hard coded examples – but we could be using variables in these statements

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Mysql Select Example

• We use a SELECT statement to grab data from a certain table and then put the result into a variable ready to analyse…

$result = mysql_query(“SELECT * FROM players WHERE age<35”);

• However now result has all the info we want inside it… how are we going to extract it in the form we want?

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mysql_fetch_row()• mysql_This function gets a result row as an enumerated array.• subsequent calls to mysql_fetch_row() would return the next row

in the result set, or FALSE if there are no more rows.<? mysql_connect(“mysql_address", "mysql_user", "mysql_pass"); mysql_select_db(“dbname");

$result = mysql_query("SELECT name, age FROM players");

while ($player = mysql_fetch_array($result)) {

print “Player $player[name] is “;print “$player[age] years old”;

}

mysql_free_result($result);?>

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mysql_num_rows()

• mysql_num_rows() returns the number of rows in a result set. This command is only valid for SELECT statements.

mysql_query(“SELECT * FROM players WHERE age<35);print mysql_num_rows().“players are younger than 35";

• It’s a great function for when you need to loop round all the results in your query, or just to know how many matches you got

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mysql_rows_affected()• mysql_affected_rows() returns the number

of rows affected by the last INSERT, UPDATE or DELETE query associated with. For example:

mysql_query("DELETE FROM mytable WHERE id < 10");

print "Records deleted: ".mysql_affected_rows()."<BR>";

• N.b. this function does not work with SELECT statements - only on statements which modify records.

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A db_connect Function

• This function can be used in scripts to connect to a database. Put it in a file called db_connect.php in your include path

<?php function db_connect($db_name){ $host_name = "localhost:3306"; $user_name = "xxxxx"; $password = "yyyyy"; $db_link = mysql_connect($host_name, $user_name, $password) or die("Could not connect to $host_name"); mysql_select_db($db_name) or die("Could not select database $db_name"); return $db_link;} ?>

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The SELECT Command

• There are many other variations of the select command.

• Example: finding the number of records in a table assuming a primary key called id:

• Can also perform searching using the WHERE option

SELECT COUNT(id) FROM table_name

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MySQL Functions (1)

• How many rows are there ?

• Can use COUNT(marks) instead of COUNT(*)

SELECT COUNT(*) FROM marks;

+----------+| COUNT(*) |+----------+| 5 |+----------+1 row in set (0.00 sec)

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MySQL Functions (2)

• What is the sum of all the marks?SELECT SUM(mark) FROM marks;

+-----------+| SUM(mark) |+-----------+| 373 |+-----------+1 row in set (0.00 sec)

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MySQL Functions (3)

• What is the average mark?SELECT AVG(mark) FROM marks;

+-----------+| AVG(mark) |+-----------+| 74.6000 |+-----------+1 row in set (0.00 sec)

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MySQL Functions (4)

• What is the minimum mark?SELECT MIN(mark) FROM marks;

+-----------+| MIN(mark) |+-----------+| 60 |+-----------+1 row in set (0.00 sec)

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MySQL Functions (5)

• What is the maximum mark?SELECT MAX(mark) FROM marks;

+-----------+| MAX(mark) |+-----------+| 86 |+-----------+1 row in set (0.00 sec)

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Entering commands• Updating a record

– UPDATE names SET lastName = 'Stone'WHERE id=3;

– SELECT * FROM names;

mysql> UPDATE names SET lastName = 'Stone' WHERE id=3;Query OK, 1 row affected (0.28 sec)Rows matched: 1 Changed: 1 Warnings: 0mysql> SELECT * FROM names;+----+-----------+------------+| id | firstName | lastName |+----+-----------+------------+| 1 | Fred | Flintstone || 2 | Barney | Rubble || 3 | Ralph | Stone |+----+-----------+------------+3 rows in set (0.00 sec)mysql>

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The DROP Command

• To delete databases and tables use the DROP command

• Examples– DROP DATABASE db_name;– DROP DATABASE IF EXISTS db_name;– DROP TABLE table_name;– DROP TABLE IF EXISTS table_name;

Note: Don't confuse DROP with DELETE which deletes rowsof a table.

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The WHERE Clause• Select rows according to some criterion

SELECT * FROM marks WHERE studentID > 1 AND studentID < 5;

+-----------+------------+-----------+------+| studentID | first_name | last_name | mark |+-----------+------------+-----------+------+| 2 | Bill | James | 67 || 3 | Carol | Smith | 82 || 4 | Bob | Duncan | 60 |+-----------+------------+-----------+------+3 rows in set (0.01 sec)

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The WHERE Clause• Select rows with marks >= 80

SELECT * FROM marks WHERE mark >= 80;

+-----------+------------+-----------+------+| studentID | first_name | last_name | mark |+-----------+------------+-----------+------+| 3 | Carol | Smith | 82 || 5 | Joan | Davis | 86 |+-----------+------------+-----------+------+2 rows in set (0.00 sec)

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The ORDER BY Clause• Select rows according to some criterion

SELECT * FROM marks ORDER BY mark DESC;

+-----------+------------+-----------+------+| studentID | first_name | last_name | mark |+-----------+------------+-----------+------+| 5 | Joan | Davis | 86 || 3 | Carol | Smith | 82 || 1 | Fred | Jones | 78 || 2 | Bill | James | 67 || 4 | Bob | Duncan | 60 |+-----------+------------+-----------+------+5 rows in set (0.00 sec)

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Searching Using LIKE (1)

• LIKE is used to search a table for values containing a search string:

• There are two wild-card characters used to specify patterns:– _ matches a single character– % matches zero or more characters

• Can also use NOT LIKE• Searching is case insensitive

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Searching Using LIKE (2)

• Example: last names in marks table that begin with J

• Example: first names that have 3 letters

SELECT * FROM marks WHERE last_name LIKE 'J%';

SELECT * FROM marks WHERE first_name LIKE '_ _ _';

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employee_db.sql (1)CREATE TABLE employees ( employeeID SMALLINT NOT NULL, name VARCHAR(20) NOT NULL, position VARCHAR(20) NOT NULL, address VARCHAR(40) NOT NULL, PRIMARY KEY (employeeID));INSERT INTO employees VALUES (1001, 'Fred', 'programmer', '13 Windle St');INSERT INTO employees VALUES (1002, 'Joan', 'programmer', '23 Rock St');INSERT INTO employees VALUES (1003, 'Bill', 'manager', '37 Front St');

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employee_db.sql (2)CREATE TABLE jobs ( employeeID SMALLINT NOT NULL, hours DECIMAL(5,2) NOT NULL,);INSERT INTO jobs VALUES (1001, 13.5);INSERT INTO jobs VALUES (1002, 2);INSERT INTO jobs VALUES (1002, 6.25);INSERT INTO jobs VALUES (1003, 4);INSERT INTO jobs VALUES (1001, 1);INSERT INTO jobs VALUES (1003, 7);INSERT INTO jobs VALUES (1003, 9.5);

Employee_id name position address

1001 Fred Programmer 13 Windle St

1002 Joan Programmer Rock St

1003 Bill manager 37 Front ST

Database Tables

Employee_id hours

1001 13.5

1002 2

1002 6.25

1003 4

1001 1

1003 7

1003 9.5

Employees tableJobs table

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Select Queries With Joins (1)• Cartesian product query

SELECT * FROM employees, jobs;

+------------+------+------------+--------------+------------+-------+| employeeID | name | position | address | employeeID | hours |+------------+------+------------+--------------+------------+-------+| 1001 | Fred | programmer | 13 Windle St | 1001 | 13.50 || 1002 | Joan | programmer | 23 Rock St | 1001 | 13.50 || 1003 | Bill | manager | 37 Front St | 1001 | 13.50 || 1001 | Fred | programmer | 13 Windle St | 1002 | 2.00 || 1002 | Joan | programmer | 23 Rock St | 1002 | 2.00 || 1003 | Bill | manager | 37 Front St | 1002 | 2.00 || 1001 | Fred | programmer | 13 Windle St | 1002 | 6.25 || 1002 | Joan | programmer | 23 Rock St | 1002 | 6.25 || 1003 | Bill | manager | 37 Front St | 1002 | 6.25 |

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Select Queries With Joins (2)• Cartesian product query (continued)| 1001 | Fred | programmer | 13 Windle St | 1003 | 4.00 || 1002 | Joan | programmer | 23 Rock St | 1003 | 4.00 || 1003 | Bill | manager | 37 Front St | 1003 | 4.00 || 1001 | Fred | programmer | 13 Windle St | 1001 | 1.00 || 1002 | Joan | programmer | 23 Rock St | 1001 | 1.00 || 1003 | Bill | manager | 37 Front St | 1001 | 1.00 || 1001 | Fred | programmer | 13 Windle St | 1003 | 7.00 || 1002 | Joan | programmer | 23 Rock St | 1003 | 7.00 || 1003 | Bill | manager | 37 Front St | 1003 | 7.00 || 1001 | Fred | programmer | 13 Windle St | 1003 | 9.50 || 1002 | Joan | programmer | 23 Rock St | 1003 | 9.50 || 1003 | Bill | manager | 37 Front St | 1003 | 9.50 |+------------+------+------------+--------------+------------+-------+21 rows in set (0.01 sec)

The cartesian product query is rarely what we want.

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Select Queries With Joins (3)• Substitution

+------+-------+| name | hours |+------+-------+| Fred | 13.50 || Joan | 2.00 || Joan | 6.25 || Bill | 4.00 || Fred | 1.00 || Bill | 7.00 || Bill | 9.50 |+------+-------+7 rows in set (0.00 sec)

Here we are replacing the employeeID numbers in the jobs table by the employee's

name

SELECT name, hours FROM employees, jobs WHEREemployees.employeeID = jobs.employeeID;

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Select Queries With Joins (4)

• Entries only for Fred

+------+-------+| name | hours |+------+-------+| Fred | 13.50 || Fred | 1.00 |+------+-------+2 rows in set (0.00 sec)

SELECT name, hours FROM employees, jobs WHEREemployees.employeeID = jobs.employeeID ANDname = 'Fred';

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Select Queries With Joins (5)• Total hours worked for each person

+------+------------+| name | SUM(hours) |+------+------------+| Bill | 20.50 || Fred | 14.50 || Joan | 8.25 |+------+------------+3 rows in set (0.00 sec)

SELECT name, SUM(hours) FROM employees, jobsWHERE employees.employeeID = jobs.employeeIDGROUP BY name;

Viewing The Table Structure

mysql> DESCRIBE students;

+------------+-------------+------+-----+---------+----------------+| Field | Type | Null | Key | Default | Extra |+------------+-------------+------+-----+---------+----------------+| num | int(11) | NO | PRI | NULL | auto_increment || f_name | varchar(48) | YES | | NULL | || l_name | varchar(48) | YES | | NULL | || student_id | int(11) | YES | | NULL | || email | varchar(48) | YES | | NULL | |+------------+-------------+------+-----+---------+----------------+

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Example: data_in.php

Putting data into DatabaseStudent Database: data_in.php

<html><head><title>Putting Data in the DB</title></head><body><?php /*insert students into DB*/if(isset($_POST["submit"])) { $db = mysql_connect("mysql”, ”CSE382"); mysql_select_db("CSE382");

$date=date("Y-m-d"); /* current date in the right format */

$sql="INSERT INTO students VALUES(NULL,'“ . $_POST[“f_name"] . "','“ . $_POST["l_name"] . "',“ . $_POST["student_id"] . ",'“ . $_POST["email"] . "','“ . $date . "',“ . $_POST["gr"] . ")"; /* construct the query */

mysql_query($sql); mysql_close();

echo"<h3>Thank you. The data has been entered.</h3> \n"; echo'<p><a href="data_in.php">Back to registration</a></p>‘ .

“\n”; echo'<p><a href="data_out.php">View the student

lists</a></p>‘ .”\n”; }

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Student Database: data_in.phpelse {?> <h3>Enter your items into the database</h3><form action="data_in.php" method="POST">First Name: <input type="text" name=“f_name“ /> <br/>Last Name: <input type="text" name=“l_name“ /> <br/>ID: <input type="text" name=“student_id“ /> <br/>email: <input type="text" name=“email“ /> <br/>Group: <select name="gr"> <option value ="1">1</option> <option value ="2">2</option> <option value ="3">3</option> <option value ="4">4</option> </select><br/><br/><input type="submit" name="submit“ /> <input type="reset“ /></form><?php }?></body></html>

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Example data_out.php

Getting Data Out from DatabaseStudent Database: data_out.php

<html><head><title>Getting Data out of the DB</title></head><body><h1> Student Database </h1><p> Order the full list of students by <a href="data_out.php?order=date">date</a>,<href="data_out.php?order=student_id">id</a>, orby <a href="data_out.php?order=l_name">surname</a>.</p><p><form action="data_out.php" method="POST">Or only see the list of students in group <select name="gr"> <option value ="1">1</option> <option value ="2">2</option> <option value ="3">3</option> <option value ="4">4</option></select><br/><input type="submit" name="submit“ /></form></p>

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Student Database: data_out.php

<?php /*get students from the DB */$db = mysql_connect("mysql",“CSE382");mysql_select_db(“CSE382", $db);

switch($_GET["order"]){case 'date': $sql = "SELECT * FROM students ORDER BY date"; break;case ‘student_id': $sql = "SELECT * FROM students ORDER BY student_id"; break;case ‘l_name': $sql = "SELECT * FROM students ORDER BY l_name"; break;default: $sql = “SELECT * FROM students”; }if(isset($_POST["submit"])){ $sql = “SELECT * FROM students WHERE gr=“ . $_POST["gr"];}

$result=mysql_query($sql);while($row=mysql_fetch_array($result)){ echo "<h4> Name: “ . $row["l_name"] . ', ‘ . $row["f_name"] . "</h4> \n"; echo "<h5> ID: “ . $row[“student_id"] . "<br/> Email: “ . $row["email"] .

"<br/> Group: “ . $row["gr"] . "<br/> Posted: “ . $row["date"] . "</h5> \n";}mysql_free_result($result);mysql_close();?></body></html>

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Poll Example

• Simple form that gives a list of choices for the poll

• Save poll results in a database• Don't allow user to do the poll more than

once from the same URL• Include a "show results" button that gives the

percentages for each entry in the list of choices

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Poll Results Database Table

CREATE TABLE poll_results( votes INT UNSIGNED NOT NULL DEFAULT 0, yes INT UNSIGNED NOT NULL DEFAULT 0);INSERT INTO poll_results VALUES(0,0);

This table keeps track of the total number ofvotes and the total number of yes votes

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IP Address Database Table

CREATE TABLE poll_ips( ip VARCHAR(30) NOT NULL, PRIMARY KEY (ip));

When a user votes the IP addressis stored in this table so that nonefrom this location can vote again

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Voting Displaysdisplay after

voting

display after trying to vote

again

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Script LogicOpen a database connectionGet user IP addressIF results button was clicked THEN display the poll resultsELSE IF submit button clicked AND vote entered THEN Get the vote from radio button IF user has already voted THEN Warn user ELSE submit the vote ENDIF display the poll resultsELSE display the poll voting formENDIFClose the connection

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poll.php (1)<?phprequire_once("db_connect.php");start_html();$ip_address = $_SERVER['REMOTE_ADDR'];$poll_question = "Do you like Java programming?";

// Table for ip addresses

$ip_table = "poll_ips";// Table for total votes and total yes votes

$vote_table = "poll_results";$db_link = db_connect("web_db");

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poll.php (2)if (isset($_REQUEST['results'])){ display_poll_results($poll_question, $vote_table);}elseif ( isset($_REQUEST['submit']) && isset($_REQUEST['vote']) ){ $vote = $_REQUEST['vote']; if ( has_voted($ip_address, $ip_table) ) { echo '<p class="warn">Someone at your location has already votes</p>'; }

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poll.php (3) else { submit_poll_vote($ip_address, $vote, $vote_table, $ip_table); } display_poll_results($poll_question, $vote_table);else{ display_poll_form($poll_question);}mysql_close($db_link);end_html();exit(0);

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poll.php (4)function start_html(){?><html><head><title>Web Poll using MySQL</title> <style type="text/css"> .warn {font-weight: bold; font-size: small; color: #FF0000 } .bg1 { background-color: #AEC6D9 } .bg2 { background-color: #0099CC } </style></head><body><?php}

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poll.php (5)function end_html(){ ?> </body> </html> <?php}

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poll.php (6)

function has_voted($user_ip, $ip_table){ // return false // comment when testing is complete

$query = "SELECT ip FROM $ip_table WHERE ip = '$user_ip'"; $result = mysql_query($query) or die("CheckIP query failed"); return mysql_num_rows($result) > 0;}

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poll.php (7)

function display_poll_form($poll_question){ $script_url = $_SERVER['PHP_SELF']; ?> <h2>Poll Question</h2> <h3><?php echo $poll_question?></h3> <form method="POST" action= "<?php echo $script_url ?>"> <input type="radio" name="vote" value=1 />Yes<br /> <input type="radio" name=vote" value=0 />No<br /> <input type="submit" name="submit" value="Submit"/> <input type="submit" name="results value="Results"/> </form> <?php}

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poll.php (8)

function display_poll_results($poll_question, $vote_table){ $total_votes = 0; $total_yes = 0; $total_no = 0; $percent_yes = 0; $percent_no = 0; $query = "SELECT votes, yes FROM $vote_table"; $result = mysql_query($query) or die("Query failed"); if ( mysql_num_rows($result) == 1 ) { $row = mysql_fetch_assoc($result); $total_votes = $row['votes']; $total_yes = $row['yes']; $total_no = $total_votes - $total_yes; }

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poll.php (9)

if ($total_votes != 0) { $percent_yes = round( (($total_yes / $total_votes)*100), 1); $percent_no = round( (100 - $percent_yes), 1); }

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poll.php (10)

?> <h2>Poll Results</h2> <table border="0" cellpadding="5"> <tr> <td class="bg2" colspan="3"><b> <?php echo $poll_question ?></b></td> </tr>

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poll.php (11) <tr> <td class="bg1">Yes</td> <td class="bg1"><?php echo $percent_yes ?> % </td> <td class="bg1"><?php echo $total_yes ?> votes </td> </tr> <tr> <td class="bg1">No</td> <td class="bg1"><?php echo $percent_no ?> %</td> <td class="bg1"><?php echo $total_no ?> votes </td> </tr> </table> <p><a href="seeit.php">View Source</a></p> <?php mysql_free_result($result);}

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poll.php (13)

function submit_poll_vote($user_ip, $user_vote, $vote_table, $ip_table){ $total_votes = 0; $total_yes = 0;

// Get the current total votes and total yes vote

$query = "SELECT votes, yes FROM $vote_table"; $result = mysql_query($query) or die("Query failed");

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poll.php (14)

if ( mysql_num_rows($result) == 1 ) { $row = mysql_fetch_assoc($result); $total_votes = $row['votes']; $total_yes = $row['yes']; } else // initialize the poll { $query = "INSERT INTO $vote_table SET votes = '0', yes ='0'"; $result = mysql_query($query) or die("<p>Query failed</p>"); }

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poll.php (15)

// Update total votes and total yes votes $total_yes = $total_yes + $user_vote; // 1 = yes $total_votes++; $query = "UPDATE $vote_table SET votes = '$total_votes', yes = '$total_yes'"; $result = mysql_query($query) or die("<p>Update vote failed</p>\n");

// Record the browser ip so user can only vote once $query = "INSERT INTO $ip_table SET ip = '$user_ip'"; $result = mysql_query($query) or die("<p>Insertion of ip failed</p>\n");}

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Authentication with MySQL

• Instead of using basic authentication that is implemented using HTTP headers it is better to use a database to store user names and passwords.

• A session variable can be used to identify a valid user.

• First create a data base with fields for the user id and the password:

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login.sql (user database)

USE web_db;DROP TABLE IF EXISTS login;

CREATE TABLE login( name VARCHAR(10) NOT NULL, password VARCHAR(30) NOT NULL, PRIMARY KEY (name));# insert a few users and encrypt the passwords

INSERT INTO login VALUES ('test', PASSWORD('123'));INSERT INTO login VALUES ('look', PASSWORD('kool'));INSERT INTO login VALUES ('Fred', PASSWORD('Jones'));

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user database

mysql> use web_db;Database changedmysql> SELECT * FROM login;+------+------------------+| name | password |+------+------------------+| test | 773359240eb9a1d9 || look | 7d74a0bb51520618 || Fred | 64099a8d551f7d81 |+------+------------------+3 rows in set (0.00 sec)mysql>

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Login script logic

Start a sessionIF username AND password were submitted THEN Check that these values are alphanumeric. IF not THEN set them to empty strings END IF IF there is a matching row in login table THEN Set a 'valid-user' session variable having value the username as value. ELSE Display login page with form to login ENDELSE Display login page with form to loginEND

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login.php (1)<?phprequire_once("db_connect.php");session_start();if (isset($_REQUEST['userid'] && isset($_REQUEST['password'])){ // Check for alphanumeric values

$id = ereg("^[a-zA-Z0-9]+$", $_REQUEST['userid']) ? $_REQUEST['userid'] : ""; $pass = ereg("^a-zA-Z0-9]+$",$_REQUEST['password']) ? $_REQUEST['password'] : "";

// now try to authenticate these values

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login.php (2) if (isAuthentic($id, $pass)) { $_SESSION['valid_user'] = $id; display_members_page(); } else { display_login_page("Invalid login, try again"); }else // first time so display form to login{ display_login_page("Please log in");}?>

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login.php (3)<?phpfunction isAuthentic($id, $password){ $db_link = db_connect("web_db");

$query = "SELECT * FROM login WHERE name like '$id'" . "AND password like PASSWORD('$password')";

$result = mysql_query($query, $db_link); $valid = mysql_num_rows($result) > 0;

mysql_free_result($result); mysql_close($db_link); return $valid;}?>

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login.php (4)<?phpfunction display_login_page($message){?><html><head><title>Members Login Page</title></head><body><h1>Login Page</h1><h2><?php echo $message ?></h2><form method="POST"><table border="1"><tr><td>

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login.php (5) <table border="0"> <tr><td>User Name:</td> <td><input type="text" name="userid"></td</tr> <tr><td>Password:</td> <td><input type="password" name="password"></td> </tr> <tr><td colspan=2 align=center> <input type="submit" value="Log in"></td></tr> </table></td></tr></table></form></body></html><?php}?>

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login.php (6)<?phpfunction display_members_page(){?><html><head><title>Members Page</title></head><body>You have successfully logged in as user<strong><?php echo $_SESSION['valid-user']?></strong><p><a href="members.php?<?php echo SID?>">Memberpages</a><br><a href="logout.php?<?php echo SID?>">Logout</a></p></body></html><?php } ?>

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logout.php<?phpsession_start();unset($_SESSION['valid-user']);session_destroy();?><html><head><title>Logout Page</title></head><body><h1>Logout Page</h1>If you were logged in you have been logged out<p><a href="login.php">Login Again</a></p></body></html>

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members.php (1)<?phpsession_start();if (! isset($_SESSION['valid-user'])){ ?><html><head><title>Login Error</title></head><body><h1>Login Error</h1>You are not authorized to view this page, please <a href="login.php?<?php echo SID?>">login</a></body></html><?phpexit();}?>

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members.php (2)<html><head><title>Member Page</title></head><body><h1>Member Page</h1>This is a member page.<br>You are logged in as user<strong><?php echo $_SESSION['valid_user']?></strong>.<p><a href="logout.php?<?php echo SID?>">Logout</a></p></body></html>

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Some SQL data types (1)

• Each entry in a row has a type specified by the column.

• Numeric data types– TINYINT, SMALLINT, MEDIUMINT,– INT, BIGINT– FLOAT(display_length, decimals)– DOUBLE(display_length, decimals)– DECIMAL(display_length, decimals)

• NUMERIC is the same as DECIMAL

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Some SQL data types (2)

• Date and time types– DATE

• format is YYYY-MM-DD

– DATETIME• format YYYY-MM-DD HH:MM:SS

– TIMESTAMP• format YYYYMMDDHHMMSS

– TIME• format HH:MM:SS

– YEAR• default length is 4

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SQL data types (3)

• String types– CHAR

• fixed length string, e.g., CHAR(20)

– VARCHAR• variable length string, e.g., VARCHAR(20)

– BLOB, TINYBLOB, MEDIUMBLOB, LONGBLOB

• same as TEXT, TINYTEXT ...

– ENUM• list of items from which value is selected

Design Report Outline• Preface • Introduction• Detail about the company and work process• Detail about the system you will be working• System Specification & User Requirement• System Models: Use Case, Sequential diagram, Data Flow diagram, UML,

Structured Chart• Data Modeling: Database requirement, ER-Diagram, Empty tables, Relational

Schema Diagram• User Interface Design• Conclusion• Bibliography• Appendices: HW, DB, logical organization• Index: index of diagrams, Tables, Functions etc.