Show and discuss library designs. Other examples.
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Creating databases for web
applications
Library. New example: student
database.
Homework: Complete class
example. Catch up on source
postings. Do creation and simple
entry and retrieval for a database.
Library?
• Show information (ERD) and process
(DFD)
Simple example
• Students: name, gpa, department
• http://socialsoftware.purchase.edu/jeanine.
meyer/studentexample/showstudents.php
• http://socialsoftware.purchase.edu/jeanine.
meyer/studentexample/showdepartments.
php
• http://socialsoftware.purchase.edu/jeanine.
meyer/studentexample/enterstudent.html
Storyboard
createtable
enterstudent.html
enterstudent.php
showstudents.php
showdepartments.php
Note
• Plenty to add
– improve look of enterstudent.html
– provide better feedback
– add edit student info function, probably based
on displaying a list
– add more display functions, such as top
student in each department, all students with
averages over a certain amount, ?
– more information
create the one table
Fields
id
name
department
GPA
So what should the SQL and what should all
the code be?
Write it down.
<?php
require("connectcode.php");
$tname = "students";
$fields = "sid INT NOT NULL AUTO_INCREMENT
PRIMARY KEY, sname CHAR(30), sgpa FLOAT(5,4),
sdept CHAR(30)";
$query = "DROP TABLE students";
mysqli_query($link,$query);
$query = "CREATE TABLE $tname ($fields)";
if (mysqli_query($link,$query)) {
print ("The table, $tname, was created
successfully.<br>\n");
}
else {
print ("The table, $tname, was not created. <br>\n");
}
mysqli_close($link);
?>
Adding a record to the students
table
• The enterstudent.html file does not use
php. It displays a form that invokes
enterstudent.php using the action attribute
on the form.
• Think about what the html file would look
like….
enterstudent.html
<html><head><title>Input student </title></head>
<body>
<form action="enterstudent.php">
Student Name <input type="text"
name="sn"/><br/>
Department <input type="text" name="sd"><br/>
GPA <input type="input" name="sgpa" /><br/>
<input type="submit" value="STORE"/>
</form> </body> </html>
Note
• The names of the input fields of the form do not have to
be consistent with the names of the fields in the
database table.
• Extra credit opportunity: Report on Ruby on Rails. This is
an alternative to html and php that produces code that
uses these connections.
• The php code does insert slashes to prevent problems
with names such as O'Bama.
• … does check that gpa is a number. Could add a tighter
check that it is a number between 0 and 5 (?).
• The 0 for the sid field is a placeholder. The stored sid will
be the autoincremented value.
enterstudent.php
<?php
require("connectcode.php");
$sn =$_GET['sn'];
$sn = ADDSLASHES($sn);
$sd=$_GET['sd'];
$sd = ADDSLASHES($sd);
$sgpa = $_GET['sgpa'];
if (!is_numeric($sgpa)) {
print ("Bad GPA data."); }
else { $query="INSERT INTO students VALUES (";
$query.="'0','$sn',$sgpa,'$sd')";
print ("query is $query. ");
if (mysqli_query($link,$query)) {
print ("Student record added successfully"); }
Else {
print ("failure to add student record "); } }
mysqli_close($link); //this depends on db link
?>
Note
• Order of fields is important for the
VALUES form of the INSERT statement.
• There is another form:
INSERT INTO students SET …
Extra credit: research and see what works.
showstudents.php
<html> <head><title>List contents of students
table</title></head><body>
<?php
require("connectcode.php");
$query="SELECT * FROM students";
$result=mysqli_query($link, $query);
print("<table border='1'>");
print("<tr><th>Student</th><th>Department</th><th>GPA
</th></tr>");
while ($row=mysqli_fetch_array($result)) {
print("<tr>");
print("<td> ".$row['sname']."</td>");
print ("<td>".$row['sdept'] ."</td>");
print ("<td>".$row['sgpa']."</td>");
print ("</tr>"); }
mysqli_close($link);
?>
</table> </body> </html>
Another enhancement
• What to do when the table gets big?
• Implement 'paging'
• Put in buttons, perhaps using an a tag with a
query string giving the page value
• The SELECT statement has a LIMIT feature
– SELECT …. LIMIT 1, 10
– SELECT …. LIMIT 11, 10
– $query = "SELECT ….. LIMIT " . $next . ", 10 "
• Opportunity for research.
showdepartments
• Aggregate functions
– count
– average
– sum
–…
• Use names (aliases) in the SELECT
statement
• ORDER BY
• GROUP BY
from showdepartments.php
<?php
require("connectcode.php");
$query="SELECT sdept, AVG(sgpa) as a, COUNT(*) as c FROM
students GROUP BY sdept ORDER BY a DESC";
$result=mysqli_query($link, $query);
print("<table border='1'>");
print("<tr><th>Department</th><th>Average GPA </th><th>COUNT
</th></tr>");
while ($row=mysql_fetch_array($result)) {
print("<tr>");
print("<td> ".$row['sdept']."</td>");
print ("<td>".$row['a'] ."</td>");
print ("<td>".$row['c']."</td>");
print ("</tr>");
}
mysqli_close($link);
?>
</table>
Variation
• Impose condition on the GROUPed data
• http://socialsoftware.purchase.edu/jeanine.
meyer/studentexample/showbigdepartmen
ts.php
• Change QUERY to
$query="SELECT sdept, AVG(sgpa) as a,
COUNT(*) as c FROM students GROUP
BY sdept HAVING c>1 ORDER BY a
DESC";
SELECT
• WHERE condition and JOIN conditions
are done on individual records.
• HAVING condition is on GROUPed data.
• Look at my examples AND use sources.
Caution
The word 'design' may refer to
• Design (plan, structure, organization,
definition) of the database and the
application
• The look of an application
• One of my examples: the content of the
product being produced is the design of a
grid using pre-defined units.
Systems design
• Focus on information
– what is the information and how do [things] relate
– Entity relationship diagramming is a tool
– Information may exist already in the organization
• organizations may have products, perhaps customized, to
hold their information
• includes dates, versions, owners, etc.
• Focus on function of application(s)
– who does what
– … using what information
System design
• slow down rush to implement
• [start] documentation
• Design and documentation may change as
system is being built, deployed, refined….
• Still, goal is to decrease bugs
ER diagram
• Database holds
– Tables. Table represents one type of entity
Row in table holds information on one example of the entity
– Row in table made up of
• Attributes (aka fields)
• Lines connecting tables indicate occurrence of attribute
in one table that points to a row in another table (or that
table)
– What is the pointer? The id of the row. This is called a foreign
key.
• One mark of good design is robustness: ease of
changing over time.
File upload
• What if the application requires users to
upload files?
– and asking them to use an ftp program not
appropriate
• The ISP may not permit this. CTS put
restrictions on us. Why?
fileupload1.html
<html>
<head><title>Get file name </title></head><body>
<form action="fileupload2.php" method="post"
enctype="multipart/form-data">
<label for="file">Filename:</label>
<input type="file" name="file" id="file" />
<br />
<input type="submit" name="submit" value="Submit" />
</form>
</body> </html>
fileupload2.php
<?php
if ((($_FILES["file"]["type"] == "image/gif")
|| ($_FILES["file"]["type"] == "image/jpeg")
|| ($_FILES["file"]["type"] == "image/pjpeg"))
&& ($_FILES["file"]["size"] < 200000))
{
if ($_FILES["file"]["error"] > 0)
{
echo "Return Code: " . $_FILES["file"]["error"] . "<br />";
}
else
fileupload2.php, cont.
{ echo "Upload: " . $_FILES["file"]["name"] . "<br />";
echo "Type: " . $_FILES["file"]["type"] . "<br />";
echo "Size: " . ($_FILES["file"]["size"] / 1024) . " Kb<br />";
echo "Temp file: " . $_FILES["file"]["tmp_name"] . "<br />";
if (file_exists($_FILES["file"]["name"]))
{ echo $_FILES["file"]["name"] . " already exists. ";
}
else
{
$target = "uploads/";
$target .= $_FILES["file"]["name"];
move_uploaded_file
($_FILES["file"]["tmp_name"],$target);
echo "Stored as: " . $target;
} } }
fileupload2.php
else
{
echo "Invalid file";
}
?>
Classwork/Homework
Application: database for movies
• Tables: movies,
people_having_role_in_movie, people,
nominations, ?
• What processes would you want?
– what maintenance functions do you want to
have?
– what questions would you want to ask
JOINs
• Some questions require data from multiple
tables.
• Tables can be connected by conditions,
most typically connecting foreign keys with
primary keys.
• SELECT …. FROM table1 as t JOIN
table2 as s ON t.fid = s.fid
– The fid field may be primary key in table1. It is
referenced by a field in table2.
Multiple tables
• SELECT p.pname, n.award FROM people
as p JOIN roles as r ON p.pid = r.pid JOIN
nominations as n ON r.rid = n.rid WHERE
n.award IN (“BEST LEAD ACTOR”, “BEST
LEAD ACTRESS”, “BEST SUPPORTING
ACTOR”, “BEST SUPPORTING
ACTRESS”)
Tasks
• List all movies by name, ordered by date
• List all people by name with roles in a
given movie, named $moviename
• List all directors (by name), with movie (by
name) ordered by movie name
• List all movies by name in which someone
was nominated for Best Lead Actor
• List all movies by name in which someone
was nominated for an acting category
– Best Lead Actor, Best Lead Actress, Best
Supporting Actor, Best Supporting Actress
More
• List movie name, person name, award
name ordered by movie name
• List movie name, number of people
nominated, ordered from high to low
– EXTRA CREDIT: figure out how not to count
multiples for awards that have multiples (such
as producer, technical awards
• List winners: movie name, person name,
award
Research
• Some questions require consideration of
absent records
– What movies were nominated (had people
nominated) for Best Movie but not Best
Director
–?
• Look up and study examples of LEFT
JOINS
Classwork/homework
• Devise [more] SQL statements
• Keep experimenting with creating tables,
simple html and php scripts for data entry
and for display.
