Download Lecture Six - Helios Hud

Website Development
Working with Databases
What you will achieve today!
•Connecting to mySql
•Creating tables in mySql
•Saving data on a server using mySql
•Getting data from the server using
mySql
Reminder of the general process
: Customer
browser
web server
scripting
language
database
request service
access page
interpret
set data
get data
get data
return html
present html
today’s
emphasis
The database
• A relational database is made up of tables (sometimes
known as relations)
• Tables are made up of rows (records) and columns (fields,
attributes)
• Table structure is described in terms of its columns
(fields, attributes) E.g. cars (make, model, doors, fuel,
cost)
• Tables are usually linked to other tables via relationships
Outline
• MySQL
• PHPMyAdmin
• Simple database communication using PHP
MySQL is a relational database management system.
A relational database stores data in separate tables rather than
putting all the data in one big storeroom. This adds speed and
flexibility. The tables are linked by defined relations making it
possible to combine data from several tables on request. The SQL
part of MySQL stands for "Structured Query Language" - the
most common standardized language used to access databases.
http://www.mysql.com/information/index.html
MySQL
•
•
•
•
•
Lightweight
Easy to administer
Runs on low power machines
Great for development
Not quite there when compared to Oracle, MS
SQL Server or IBM DB2 but coming along fast
(http://www.devx.com/dbzone/Article/20743 )
Installing on your machine
• If you are going to work at home with
PHP/MySQL I recommend one of the
distributed packages for web development
• The one we use at uni is called Wamp and is
available from
http://www.en.wampserver.com/
• There are other alternatives
GUI
• Most common is phpMyAdmin
• Hermes link is
– http://hermes.hud.ac.uk/phpMyAdmin/
– Normal username and password
• Let’s have a look at it…
The Four SQL Commands
•
•
•
•
SELECT
INSERT
UPDATE
DELETE
• These only affect values in the database, not
the structure, but once you know these four
you are set for life*
* not guaranteed
SELECT
• The example table is called "Cars"
• Each record is made up of data describing
ID Make Model Doors Fuel and Cost
• The SQL to retrieve all rows and all columns is:-
• SELECT * FROM Cars
• The * indicates that all columns from ‘Cars’ are to be included.
• This could have been written as:-
• SELECT ID Make Model Doors Fuel and Cost FROM Cars
Query result
• The code for all (*) would result in the following being
returned
SELECT
*FROM
Cars
1 Audi A4 4 Petrol £19,300
2 Audi A3 2 Petrol £16,250
3 Audi A4 Avant 5 Petrol £20,400
4 Audi A6 4 Diesel £28,880
.
.etc
More precise
SELECT
Model FROM
Cars
A4
A3
A4 Avant
A6
.
.etc
More precise
SELECT
Model,Fuel
FROM Cars
A4 Petrol
A3 Petrol
A4 Avant Petrol
A6 Diesel
.
.etc
Conditional SQL ?
• We can use WHERE, along with = <> < > >= <=
BETWEEN and LIKE, to narrow down our search:
SELECT Model FROM
Cars WHERE
Fuel='Diesel'
A6
Corolla
Corolla
330
.
.etc
Conditional query
SELECT Model,Fuel
FROM Cars WHERE
cost<10,000
Corolla Petrol
Corolla Petrol
Corolla Petrol
Corolla Diesel
Corolla Petrol
.
.etc
Wild cards and Like
SELECT Model FROM
Cars WHERE Model
LIKE '3%'
323
323 Coupe
330
Conditional logic
SELECT Model,Fuel
A4 Avant Petrol
FROM Cars WHERE
cost BETWEEN £20,000
AND £25,000
Multiple conditions
• With AND and OR we are not limited to one
condition:
SELECT
A3 Petrol £16,250
Model,Fuel,Cost FROM
Cars WHERE
cost<20,000 AND Model
= 'Audi'
The IN Keyword
• This is a neat way of doing multiple ORs. For example, suppose we
wanted a listing of all rows where the make is “AUDI” or “ALPHA”
• We could obviously do this with an OR but we can also do it with IN.
• SELECT * FROM Cars WHERE MAKE IN (“AUDI”, “ALPHA”)
• You can have as many alternatives as you like in the brackets above.
The BETWEEN Keyword
•
We want to list all rows where cost is greater than or equal to 10000 and less
than or equal to 20000. We could do this as
•
SELECT * FROM Cars
WHERE cost >= 10000
AND cost <= 20000
•
An alternative way of writing this is to use the BETWEEN keyword.
•
SELECT * FROM Cars
WHERE cost BETWEEN 10000 AND 20000
INSERT
• INSERT INTO table_name VALUES (value1,
value2,....)
• Or
• INSERT INTO table_name (column1,
column2,...) VALUES (value1, value2,....)
UPDATE
• UPDATE table_name SET column_name = new_value
WHERE column_name = some_value
• Multiple values with a comma seperated
• UPDATE table_name SET column_name = new_value,
column_name2 = new_value2 WHERE column_name =
some_value
DELETE
• DELETE FROM table_name WHERE
column_name = some_value
Tutorial
• Go to
http://www.w3schools.com/sql/sql_tryit.asp
and ‘play’ with SELECT sql
– Try the examples on the page and create a few of
your own
• Use phpMyAdmin at
http://hermes.hud.ac.uk/phpMyAdmin to
‘play’ with a mysql database
Accessing MySQL from PHP
Connecting to PHP
• We can now write SQL and setup our MySQL
database
• But we want to be able to talk to the database
using PHP
• Its easy!
• For now simple table editing (update data,
delete etc), later database editing (create,
dump tables etc)
Creating the connection
mysql_connect($hostname, $user, $password);
Then choose a database…
mysql_select_db(‘carsDB’);
Now ask it a question…
$result = mysql_query(“SELECT * FROM Cars”);
Lets see how many results came back…
$num = mysql_num_rows($result);
Now output it to the screen…
• Options for dealing with $result
– mysql_fetch_row - returns row as enumerated
array
– mysql_fetch_array – returns row as an associative
array
• mysql_fetch_row used to be fastest, but
mysql_fetch_array is the preferred favourite
now
Output to the screen…
while($row = mysql_fetch_array($result))
{
print($row[‘Make’] . $row[‘Model’] .
$row[‘Price’] . “<br/>”);
}
Putting data into the database
• Example uses cars
database
Make
Model
Price
Smart
Roadster
14000
Rover
216si
1800
Robin
Reliant
10
Psuedo code
•
•
•
•
•
Take inputs from form
Write sql string including inputted data
Connect to database
Run sql command string
Check to see if it was successful
The form
• Example html
<form method="post" action="cars_process.php">
Make:<input name="Make" type="text" /><br/>
Model:<input name="Model" type="text" /><br/>
Price:<input name="Price" type="text" /><br/>
<input name="submit" type="submit" value="Add to
Database" />
</form>
Get data from the form
$Make = $_POST['Make'];
$Model = $_POST['Model'];
$Price = $_POST['Price'];
Create the sql string
$sql = "INSERT INTO cars (Make,Model,Price)
VALUES ('$Make','$Model',$Price)";
Connect to mysql and the database
mysql_connect('localhost','root')
or die("cant talk to mysql");
mysql_select_db(‘cars')
or die("cant connect to the database");
Run the mysql command
$result = mysql_query($sql);
Check to make sure it was successful
if(mysql_affected_rows() == 1)
{
print("yay, it worked");
}
else
{
print("something went horribly wrong!");
}
Why 2 files?
• Sometimes we need everything to be done in
one file
• E.g. I fill in a form, submit to another page,
but something went wrong, now I have to go
back and fill in everything again!
• To solve this do all the processing in one page
where the form submits to itself.
<?php
$Make = $_POST['Make'];
$Model = $_POST['Model'];
$Price = $_POST['Price'];
$submit = $_POST['submit'];
$success = 0;
if ($submit == "Save" && $Make != NULL && $Model != NULL && $Price != NULL)
{
$sql = "INSERT INTO cars (Make,Model,Price) VALUES ('" . $Make . "','" . $Model . "'," . $Price . ")";
mysql_connect('localhost','root')
or die("cant talk to mysql");
mysql_select_db(‘cars')
or die("cant connect to the database");
$result = mysql_query($sql);
if(mysql_affected_rows() == 1)
{
print("yay, it worked");
$success = 1;
}
else
{
print("something went horribly wrong!");
}
}
if($success != 1) {
?>
<form method="post" action="<?php print($_SERVER['PHP_SELF']); ?>">
Make:<input name="Make" id="Make" type="text" value="<?php print($Make); ?>" /><br/>
Model:<input name="Model" id="Model" type="text" value="<?php print($Model); ?>" /><br/>
Price:<input name="Price" id="Price" type="text" value="<?php print($Price); ?>" /><br/>
<input name="submit" type="submit" value="Save" />
</form>
<?php
}
?>
Editing data in the database
• Pseudo code
– Find the data to be changed from the database
– Output the data into an editable area (e.g. a form)
– Resubmit the data
– Update the database
Connect to the database
mysql_connect('localhost','root')
or die("cant talk to mysql");
mysql_select_db(‘cars')
or die("cant connect to the database");
$sql = "SELECT * FROM cars";
$result = mysql_query($sql);
while($row = mysql_fetch_array($result))
{
print("$row[0] $row[1] - <a
href=\"editcar.php?Make=$row[0]&Model=$row[1]&Price=$row[2]\">edit</a
><br/>");
}
$Make = $_GET['Make'];
$Model = $_GET['Model'];
$Price = $_GET['Price'];
$success = 0;
$submit = $_GET['submit'];
if($submit == "Update" && $Make != NULL && $Model != NULL && $Price != NULL)
{
$sql = "UPDATE cars SET Make='$Make' , Model='$Model' , Price=$Price WHERE Make='$Make' AND
Model='$Model'";
mysql_connect('localhost','root')
or die("cant talk to mysql");
mysql_select_db(‘cars')
or die("cant connect to the database");
$result = mysql_query($sql);
if(mysql_affected_rows() == 1)
{
print("yay, it worked");
$success = 1;
}
else
{ print("something went horribly wrong!");
}
}
if($success != 1) {
?>
<form method="get" action="<?php print($_SERVER['PHP_SELF']); ?>">
Make:<input name="Make" id="Make" type="text" value="<?php print($Make); ?>" /><br/>
Model:<input name="Model" id="Model" type="text" value="<?php print($Model); ?>" /><br/>
Price:<input name="Price" id="Price" type="text" value="<?php print($Price); ?>" /><br/>
<input name="submit" type="submit" value="Update" />
</form>
<?php
}
A whole system…
• Admin area would need
– A menu
– A page for viewing data
– A page for adding new data
– A page for editing existing data
– A page for deleting existing data