MySQL and PHP

By Trevor Adams

Topics Covered What is SQL? SQL Standards MySQL

Database Tables Queries Data Manipulation Language (DML) Data Definition Language (DDL)

MySQL and PHP Connecting to MySQL Server Using a connection Functions

What is SQL?

Structured Query Language Allows database operations Retrieve data Modify data Insert new data Remove data Create and modify tables English type syntax

SQL Standards

ANSI (American National Standards Institute) SQL is available on many platforms and products Many products implement specific features that are

exclusive A product must meet the requirements of ANSI SQL

to be considered ANSI SQL compliant Assists programmers by using a common syntax

MySQL

Available as both a commercial and open-source product

Implements the SQL standards Available on many platforms

Windows Linux Mac Unix

Available from http://www.mysql.com/

MySQL - Database

A MySQL server is capable of storing many databases

A database is generally made of a collection of related tables Each student will get one database for use with

the module Every database will be accessible by the student

that owns it

MySQL - Tables

A database is generally made up of related tables Each table will have a name that is unique within the

database A table contains records with data

StudentID Forename Surname Level

AK123900 Trevor Adams M

AB340948 Bobby Ratchet 3

AC234887 Johan Doex 2

MySQL - Queries A query performed on a database can result in data or some

kind of status A returned list of required records Whether a deletion was successful

SELECT StudentID FROM Student Returns a result set

StudentID

AK123900

AB340948

AC234887

MySQL - Queries

Queries can come in the following forms: SELECT – extracting data UPDATE – updates data DELETE – deletes data INSERT – inserts data

All of these queries can be used on the MySQL database software

Data Manipulation Language

Consists of the queries that enable the developer to modify the data contained

The SQL server processes these queries and returns a result set or a status notification

Data Definition Language

Defines a set of queries that can be used by the developer to modify the data structure CREATE TABLE ALTER TABLE DROP TABLE CREATE INDEX DROP INDEX

We shall not be covering these commands to a great extent

Use a management tool to generate these commands automatically

PHP and MySQL

PHP contains all of the functionality required to interact with MySQL servers Most PHP MySQL functions are prefixed with ‘mysql_’ Use the PHP homepage to search for mysql_ and examine

the results

MySQL is a client-server based DBMS Database management system One (or few) server(s) caters for many clients Possible for web server and DBMS server to be on the

same system

Connecting to MySQL with PHP

Use the MySQL connect routine mysql_connect($host, $user, $password) $user and $password will be your account details

mysql_connect will return a link ID $link = mysql_connect($host, $user, $password) if(!$link) { echo “Unable to connect”; }

Always check the link to ensure that the database connection was successful

Selecting a database

Once a link has been established, select a database mysql_select_db($dbname, [$link]) [] optional – uses last created $link if not

given mysql_select_db returns a Boolean indicating

status $result = mysql_select_db(“students”) If(!$result) { echo “No database”; }

Using a Connection

Once a connection has been established it is possible to execute queries

Queries always return a result Success status Result Set

Use mysql_query($query_string) to execute $query = “SELECT * FROM Students”; $result = mysql_query($query); $result will contain the desired result set or false if

not available

Using a Connection

Use functions mysql_fetch_row($result) to obtain a row from the result set Returns false when no rows left

Example: $query = “SELECT * FROM Students”; $result = mysql_query($query); While($row = mysql_fetch_row($result)){

// $row will be an array index at 0 per column }

$row will be equal to false (ending the while loop) when there are no more rows left

SQL Query Types

SELECT SELECT [fields,…] FROM [table] WHERE [criteria] ORDER

BY [field] [asc,desc]

[fields] can be * for all or field names separated by commas

[table] is the name of the table to use [criteria] is a collection of Boolean expressions that

limits returned rows E.g. Forename=‘Trevor’ AND Surname=‘Adams’

[field] denotes which field to sort by

SQL Query Types

INSERT INTO INSERT INTO [table]([fields,…] VALUES([newvalues,…])

[table] indicates which table to insert into [fields] is a comma separated list of fields that are

being used [newvalues] is comma separated list of values that

directly correspond to the [fields] E.g. INSERT INTO students(StudentID, Surname,

Forename, Level) VALUES(‘AK301390’, Adams, Trevor, M)

SQL Query Types UPDATE

UPDATE [table] SET [field=value,…] WHERE [criteria] [table] denotes the table to update [field=value,…] is a comma separated list of values

for fields [criteria] – a Boolean expression that specifies which

records to update If no criteria is given, all records would be updated

UPDATE students SET forename=‘Trevor’ WHERE StudentID=‘AK301390’ With no where clause every record in the table would be

updated with forename=‘Trevor’

SQL Query Types DELETE

DELETE FROM [table] WHERE [criteria] Simple and dangerous statements [table] to delete from [criteria] specifying records to delete

No criteria deletes all records DELETE FROM students

Removes all student records with no warning and no sympathy for mistakes.

E.g. DELETE FROM students WHERE StudentID=‘AK301390’

Deletes the student with StudentID of ‘AK301390’

Quick Example

$query = “INSERT INTO students (StudentID, Forename, Surname, Level) VALUES (‘AK301390’, ‘Trevor’, ‘Addams’, ‘M’)

$result = mysql_query($query); if(!$result) {

Echo “Insertion failed”;

} else { Echo “Record inserted”;

}

Quick Example

$query = “UPDATE students SET Surname=‘Adams’ WHERE StudentID=‘AK301390’

$result = mysql_query($query); If(!$result) {

echo “Update failed!”; } else {

echo “Update successful!”; }

Quick Example

$query = “SELECT * FROM student”; $result = mysql_query($query); If(!$result) {

echo “No result set”; } else {

while ($row = mysql_fetch_row($result)){ foreach($row as $value){

echo “$value, ”; }

} }

Useful functions Many mysql functions can take a link identifier but do not need it.

Simply uses the last one opened mysql_affected_rows ( [link_identifier] )

Returns the number of rows affected from the last query mysql_errno ( [link_identifier] )

Gets the last error number from the server mysql_error ( [link_identifier] )

Returns a string containing error information mysql_fetch_array (result [,result_type] )

Retrieves a record from a result set as an array, optional result time can be MYSQL_ASSOC, MYSQL_NUM or default MYSQL_BOTH.

Other Resources

SQL is a big topic, a walk-through tutorial will be available in the lab session

Meanwhile – take a look at the following resources: http://www.w3schools.com/sql/default.asp http://www.php.net/mysql

You can obtain MySQL free of charge from http://dev.mysql.com/downloads/ Version 5.x has just been released University currently uses 4.x