1. CS 174: Server-Side Web Programming February 14 Class Meeting
Department of Computer Science San Jose State University Spring 2018 Instructor: Ron Mak
(substitute for Fabio Di Troia)

2. Entity Integrity Constraint
No primary key column of a relational table can have null (empty) values.
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

3. Entity Integrity Constraint, cont’d
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

4. Foreign Keys
A foreign key is a column in a table that refers to a primary key column in another table.
In a relational schema, draw an arrow from the foreign key to the corresponding primary key.

5. Mapping 1:M Relationships
Mandatory
participation
on both sides.
The foreign key belongs on the
M side of the 1:M relationship.
It corresponds to the primary key
on the 1 side.
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

6. Mapping 1:M Relationships, cont’d
Optional participation
on the 1 side.
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

7. Mapping 1:M Relationships, cont’d
Optional participation
on the M side.
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

8. Mapping 1:M Relationships, cont’d
Rename a foreign key
to better reflect the
role of a relationship.
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

9. Mapping M:N Relationships
Use a
bridge relation
with two
foreign keys.
AKA:
linking table
or join table.
Example:
BELONGSTO
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

10. Mapping M:N Relationships, cont’d
Optional
participation
on both sides.
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

11. Mapping M:N Relationships, cont’d
with an
attribute.
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

12. Mapping 1:1 Relationships
Map 1:1 relationships similarly to 1:M relationships.
One table will have a foreign key pointing to the primary key of the other table.
It can be an arbitrary choice of which table has the foreign key.
Make the choice that is most intuitive or efficient.

13. Mapping 1:1 Relationships, cont’d
Table VEHICLE has the foreign key.
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

14. Referential Integrity Constraint
The value of a foreign key must either:
Match one of the values of the primary key in the referred table.
Be null.
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

15. Mapping Example #1: ER Diagram
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

16. Mapping Example #1: Relational Schema
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

17. Mapping Example #1: Sample Data
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

18. Mapping Candidate Keys
Choose one of the
candidate keys
to be the primary key.
Map the other
as non-primary.
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

19. Mapping Candidate Keys, cont’d
Generally choose
a non-composite
candidate key to be
the primary key.
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

20. Mapping Multivalued Attributes
Map the multivalued
attribute as a new table.
This becomes a 1:M
relationship with the
new table on the M side.
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

21. Mapping Derived Attributes
Do not map derived attributes.
Sample data records.
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN
As seen by the front-end application.

22. Mapping Example #2: Attributes
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

23. Mapping Unary 1:M Relationships
The table contains a
foreign key that
corresponds to its
own primary key.
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

24. Mapping Unary M:N Relationships
Use a bridge relation
where both foreign keys
refer to the primary
key of the same table.
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

25. Mapping Unary 1:1 Relationships
Map similarly
to a unary 1:M
relationship.
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

26. Mapping Multiple Relationships
Map each
relationship.
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

27. Mapping Weak Entities
Map weak entities the same way you map regular entities.
The resulting table has a composite primary key that is composed of:
The partial identifier of the table.
The foreign key corresponding to the primary key of the owner table.

28. Mapping Weak Entities, cont’d
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN
The APARTMENT table’s composite primary key
consists of AptNo (the partial key)
and BuildingID (the foreign key
corresponding the the primary key
of the owner BUILDING table).

29. Mapping Example #3: ER Diagram
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

30. Mapping Example #3: Relational Schema
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

31. Mapping Example #3: Sample Data
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

32. Mapping Example #3: Sample Data, cont’d
Database Systems
by Jukić, Vrbsky, & Nestorov
Pearson 2014
ISBN

33. ER Modeling and Relational Modeling
Why not skip ER modeling and go directly to logical modeling (creating relational schemas)?
ER modeling is better for visualizing requirements.
Certain concepts can be visualized graphically only in an ER diagram.
Every attribute appears only once in an ER diagram.
A conceptual model (ER diagram) is better for communication and documentation.

34. Start the MariaDB Database Server

35. XAMPP Home Page phpMyAdmin is a PHP-based GUI interface
to the MariaDB database server.

36. phpMyAdmin Home Page

37. Database Server Root Password
By default, there is no root password.
Set the root password using phpMyAdmin.
Go to the Users accounts tab.
Edit the root user at localhost to change its password.

38. Database Server Root Password, cont’d

39. Enable phpMyAdmin to Connect
phpMyAdmin connects to the MariaDB database server as the root user.
Now you must tell phpMyAdmin what the new root password is.
Edit the configuration file XAMPP/xamppfiles/phpmyadmin/config.inc.php
Edit the line $cfg['Servers'][$i]['password'] = 'root password';
For this class, use the database password sesame

40. Add a New Database User Name the user after yourself or your team.
Click “Add user” on the Users tab.
Use “localhost” for the host.
Tick the checkbox to create a database with the same name.

41. Create a Table in the New Database

42. Insert Data into the Table

43. Browse the Table Contents

44. MySQL Command Line Interface
~: /Applications/XAMPP/xamppfiles/bin/mysql -u supercoders -p
Enter password:
mysql> show databases;
| Database |
| information_schema |
| supercoders |
2 rows in set (0.00 sec)
mysql> use supercoders
Database changed
mysql> show tables;
| Tables_in_supercoders |
| people |
1 row in set (0.00 sec)

45. MySQL Command Line Interface, cont’d
mysql> select * from people;
| id | first | last | gender | salary |
| 101 | John | Adams | M | |
| 102 | Mary | Smith | F | |
| 105 | Helen | Troy | F | |
| 110 | Albert | Jones | M | |
4 rows in set (0.00 sec)
mysql> select * from people
-> where first = 'Helen'
-> and last = 'Troy';
| id | first | last | gender | salary |
| 105 | Helen | Troy | F | |
1 row in set (0.00 sec)
mysql>

46. Simple End-to-End Web Application!
Client side
A static HTML page the contains a form to submit a person’s first and last names.
Server side
PHP code that uses the first and last names to query a back end database.
A dynamically generated web page that contains a table of the query results.
Back end
A database table containing people data.
Demo

47. Default Web Page: index.html
people/index.html
<body>
<form action="queryDB.php"
method="get">
<fieldset>
<legend>User input</legend>
<p>
<label>First name:</label>
<input name="firstName" type="text" />
</p>
<label>Last name:</label>
<input name="lastName" type="text" />
<input type="submit" value="Submit" />
</fieldset>
</form>
</body>

48. PHP Page: queryDB.php queryDB.php Connect to the database and set $con
<body>
<h1>Query Results</h1>
<p>
<?php
$first = filter_input(INPUT_GET, "firstName");
$last = filter_input(INPUT_GET, "lastName");
try {
// Connect to the database.
$con = new PDO("mysql:host=localhost;dbname=supercoders",
"supercoders", "sesame");
$con->setAttribute(PDO::ATTR_ERRMODE,
PDO::ERRMODE_EXCEPTION);
... }
catch(PDOException $ex) {
echo 'ERROR: '.$ex->getMessage();
?>
</p>
</body>
queryDB.php
Connect to the
database and set $con
to refer to the
connection object.
If an error occurs,
throw an
exception.
PDO documentation:

49. PHP Page: queryDB.php, cont’d
try {
...
                // Constrain the query if we got first and last names.
                if ((strlen($first) > 0) && (strlen($last) > 0)) {
// Constrain the query if we got
// first and last names.
                    $query = "SELECT * FROM people ".
                             "WHERE first = '$first' ".
                             "AND   last  = '$last'";
                }
                else {
// Otherwise fetch all the rows.
                    $query = "SELECT * FROM people";  
// We're going to construct an HTML table.
print "<table border='1'>\n"; }

50. PHP Page: queryDB.php, cont’d
try {
...
                // Query the database.
                $data = $con->query($query);
                $data->setFetchMode(PDO::FETCH_ASSOC); }
Query the database to
get a result set $data.
We will fetch rows from
the result set as an
associative array of
name => value pairs.

51. PHP Page: queryDB.php, cont’d
try {
...
                // Construct the HTML table row by row.
                // Start with a header row.
                $doHeader = true;
                foreach ($data as $row) {
                                    
                    // The header row before the first data row.
                    if ($doHeader) {
                        print "        <tr>\n";
                        foreach ($row as $name => $value) {
                            print "            <th>$name</th>\n";
                        }
                        print "        </tr>\n";
                        
                        $doHeader = false;
                    } }
queryDB.php
Loop over each $row
of the result set $data.
Loop over the name => value pairs
of the first $row.
Print the $name
(the column name).

52. PHP Page: queryDB.php, cont’d
try {
...
                    // Data row.
                    print "            <tr>\n";
                    foreach ($row as $name => $value) {
                        print "                <td>$value</td>\n";
                    }
                    print "            </tr>\n";
                }
                
                print "        </table>\n";
            }
            catch(PDOException $ex) {
                echo 'ERROR: '.$ex->getMessage();
            }        
queryDB.php
Loop over the
name => value pairs
of each $row and
print the $value.