Download MySQL: Part II - Oxford University ICT Forum

Developing MySQL Database
Applications
6th IT Support Staff Conference
Andrew Slater (IT Support Officer: Phonetics & Modern Languages)
and
John Ireland (Computing Manager, Jesus College)
Workshop Synopsis
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Introduction to MySQL
Open Database Connectivity (ODBC)
Home-cooking: writing clients
Interacting with the web / PHP
Other APIs explained
Illustration: college noticeboard
Links and references
What IS MySQL?
Welcome to MySQL
• Relational Database Management
System (RDBMS)
• Open source (GNU Public
License)
• MySQL server: Windows
9x/NT/2000, Linux, Solaris,
OS/2, BSD…
• Clients can be different
platforms, both via legacy
interfaces and open standards
(e.g. ODBC)
www.mysql.com
Features and Compliance
• ANSI SQL92 (almost!) except:
– Sub-select
SELECT * FROM table1 WHERE id IN
(SELECT id FROM table2);
– SELECT INTO table…
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Multi-threaded (good multi-processor performance)
Handles large files (e.g. 200GB) efficiently
Flexible security model
Highly optimised JOINs
Performance / Benchmarks
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Comparison of competing DBMSs
Identical hardware for each test
Same platform / OS for each test
Graphs shown are summary from MySQL web site
MySQL / PostgreSQL
MySQL / Access 2000
Smart Datatypes
• AUTONUMBER fields are available: a non-revisiting
incremental field.
– In MySQL you can set the value of an AUTONUMBER
field (but beware the consequences).
• First TIMESTAMP field is automatically set to current
date/time whenever record is updated
– Last change time can be a very useful per-record property.
– Format is ‘YYYYmmddHHMMSS’, e.g. 20010621142532
Security (1)
• Username / password (and optionally client hostname)
checked before any commands are accepted;
• Different access for each operation (SELECT, INSERT,
UPDATE, DELETE, CREATE, DROP, …)
• Access is allow / deny at a global, database, table or
column level
MySQL
CLIENT
HOST
USERNAME
PASSWORD
DATABASE.
TABLE
Security (2)
• For given SQL statement, permissions are sum of:
– global ‘user’ permissions;
– permissions specific to table or column;
– database (i.e. ‘all tables’) restricted by host.
PER-DATABASE
PER-USER
PER-HOST
PER-REQUEST PRIVILEGE
PER-TABLE
PER-COLUMN
Open Database Connectivity
ODBC Overview
• ODBC provides the
application with a standard
interface to different
DBMS
APPLICATION
ODBC
ODBC Driver
MySQL
MySQL
DATA
Centralised Data
• Local application has
access to data via operating
system (e.g. local files,
shared drives, UNC path)
• ODBC gives access to data
held elsewhere, with
benefits such as
information-centric locking
and security
LOCAL
APPN
ODBC
NETWORK
ODBC
REMOTE
DATABASE
Using MyODBC
• Small, free download
from www.mysql.com;
• Install adds ‘MySQL’ to
options in control panel
(ODBC applet);
• Create a ‘Data Source
Name’ for each MySQL
database.
MS Access Connectivity
Link tables from external
databases (e.g. other Access
*.mdb files or ODBC source)
Linked data appears as
just another table
(even DLookup)
MS Access and MySQL
• Generally good, fast integration (especially compared to
Access with data on shared drive)
• Occasional (documented) caveats, e.g. saving a new record
can show all fields as #DELETED (use TIMESTAMP)
• ‘Find first’ operation can be very slow
• Transaction support and roll-back recently added
• No direct OLE support, but simple work around available
Home-cooked Clients:
the Application Programming Interface
Why Write Clients?
A client is simply the user interface:
we already write these!
• Choice of tools to generate
the UI: this choice should
not affect the user;
• Each tool has (subtly)
different emphasis;
• Clients can interact directly
with MySQL for speed /
memory benefits.
Tools to write clients
VBA / Access
Foxpro
Crystal reports
ASP / PHP / CGI
C / C++ / PERL
Java
Application
Programming
Interface
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Key features
MySQL functions
Form processing
Session handling
Demos
What’s PHP?
PHP: Hypertext Pre-processor
• “A scripting language that generates dynamic content for
the web.”
• Developed by Rasmus Lerdorf (1994)
Key features
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server-side scripting language
tight integration with MySQL
available as an Apache module
cross-platform
open source and free!
Usage stats
(source Netcraft, April 2001)
Number of
web sites
using PHP
Total (domains): 6,156,321
IP addresses:
914,146
Apache Module Usage
(Source: E-soft Inc., April 2001)
Number of
Apache web
servers
PHP, Apache and MySQL
1
6
Browser
Applications:
Speech Database
(Phonetics)
Admissions
Database
(Modern Languages)
How do I get it?
http://uk.php.net/downloads.php
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complete source code
win32 binaries [linux RPMs from Redhat]
excellent on-line documentation
FAQs, recommended books etc.
“Teach Yourself PHP4 in 24 Hours”
Matt Zandstra,SAMS publishing, 1999
Configure the web server
Changes to httpd.conf:
• AddType application/x-httpd-php .php
• DirectoryIndex index.html index.php
Restart the web server, and check it works!
Syntax
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syntax resembles C
some elements borrowed from Java, perl
user defined functions / include files
choice of tag styles:
<?php … ?>
<? … ?>
<% … %>
<script language=“php”> …</script>
welcome.php
<html>
<h1>6th ITSSC</h1>
<?php echo “Hello ITSSC delegates!”;
?>
<hr>
<?php $time = date(“H:i:s”);
printf(“The time is now %s”,$time);
?>
</html>
MySQL functions
PHP has functions that allow you to:
• connect to the database server
• run queries
• process query results
• handle errors
etc.
Connecting to MySQL
mysql_connect(hostname, username, pw)
$link = mysql_connect(“localhost”, “webuser”, “mypassword”);
or
die (“Oops - couldn’t connect”);
Selecting a database
mysql_select_db(database_name
[, link_id])
mysql_select_db(“admissions”)
or
die (“Can’t select admissions!”);
Running a query
mysql_query(query)
$result = mysql_query("SELECT lcode from languages where
lname =’French’ ");
N.B. A successful query says nothing about number of rows
returned!
Processing query results
• mysql_fetch_row(result_id)
• mysql_fetch_array (result_id)
while ($row = mysql_fetch_array ($result))
{
printf (“%s %s\n”, $row[“surname”], $row[“firstname”]);
}
Form processing
• Web databases often use forms as part of the user interface
• Form data variables automatically generate PHP variables
of the same name
Simple form
myform.html
<form action = "process.php">
Please type your name:
<input type = text name ="user">
</form>
process.php
<?php
echo “Hello $user!”;
?>
Speech database
“English Intonation in the British Isles”
Grabe, Nolan, Post (ESRC grant)
– 40 hours of speech
– 9 dialects of British English
What are sessions?
HTTP: a stateless protocol
Client 1
Web server
Client 2
Joe
Mary
1
3
5
2
4
6
Why do we need sessions?
A SESSION associates DATA with a USER for
duration of their entire visit
•e-commerce
•CUSTOM web pages for different users
(users can log in to web database)
How to store session info
1. Cookies
Cookies store client-specific data on the client
N.B. client may reject cookie!
Security issues?
Max cookie size 4k
2. Session files
•Sessions store client-specific data on the server
•Sessions are tagged with a unique session id
Session ids
Web server
Joe
Mary
37
95
37
95
Session ID
Session ID
Session management
PHP4 includes functions to:
• manage session data on the server
• generate random session ID to identify user
• saves session ID:
either
or
with a cookie (N.B. session ID only)
in the query string
Starting a session
session_start()
1. create session file in /tmp on the server
2. sends a cookie called PHPSESSID to the client (client may
refuse it)
Set-Cookie:
PHPSESSID=8d8e5a520c56e0a2e5751ae7b8c8273e; path=/
Cache-Control: no-store, no-cache, must-revalidate,
post-check=0, pre-check=0
Pragma: no-cache
Resuming a session
session_start()
An existing session is resumed if:
• client sends cookie with session id or
• session id was passed in the query string
http://mysite.com/mypage.html?PHPSESSID=xyz123
Registering variables
session_register(variable_name)
•session_register registers the variable for use in the
current session
•changes are automatically reflected in the session file
session_register(“college_name”);
session_register(“product1”);
Ending sessions
session_destroy()
Ends current session
(Gotcha: variables remain available in current script, until the
script reloaded)
session_unset()
Wipes all currently registered variables
Sessions example
<? php
session_start();
session_register(‘counter’);
// initialise a session
// register variable
$counter++;
// increment counter
echo (“You have visited this page $counter times”);
?>
• Modern Languages Admissions Database
Andrew Slater, Chris Turner, 2000
Used by colleges-based ML tutors to track admissions
process
Sessions used to provide college-specific views of
candidates / access rights
Other MySQL APIs
• MySQL ships with APIs for several common languages:
– C / C++
– PERL / PHP
– Java;
• Each API provides the same core functions such as:
– connect(), select_db(), query(), store_result(), close();
• Data types heavily dependent on language:
– garbage collection in Java
– query results returned as associative array in PERL
– lots of pointers in C.
Linux Client in C
• Install mysqlclient-3.2.23-1.i386.rpm
• Enter and compile code (add error checking etc.)
#include <stdio.h>
#include <mysql.h>
int main() {
MYSQL mdbi, *mdb = &mdbi;
MYSQL_RESULT *res;
MYSQL_ROW *row;
const char *host, *db, *user, *pwd;
int ii, nrows;
/* . . . Input values for host, user, pwd, db */
Linux Client: MySQL Core
mdb = mysql_connect(mdb, host, user, pwd);
mysql_select_db(mdb, db);
mysql_query(mdb, “SELECT * FROM Table”);
res = mysql_store_result(mdb);
nrows = mysql_num_rows(res);
for (ii = 0; ii < nrows; ii++) {
row = mysql_fetch_row(res);
printf(“%5d: %s\n”, atoi(row[0]), row[2]);
}
mysql_free_result(res);
mysql_close(mdb);
return 0;
}
• Compile: gcc
• Ready to run!
-o sample sample.c -lmysqlclient
Example:
Jesus College Noticeboard
• Central MySQL database of ‘articles’
– ‘Message Of The Day’ articles
– Announcements (read-once)
– News articles (with automatic index listing)
• MS Access front-end: familiar to administrative staff
• Integrated into website (notices and news board)
• Client added to system-wide UNIX login scripts
• Plans for Windows login client
Ex: System Overview
Web
Server
UNIX
Server
MS Access
(admin)
MySQL
Server
UNIX
Server
FIREWALL
MS Access
(admin)
UNIX
Server
Ex: MS Access front end
Ex: Web integration
Ex: UNIX client at login
More Information...
Extensive MySQL documentation at www.mysql.com
Teach yourself PHP in 24 hours, Matt Zandstra, SAMS 1999
MySQL manual, Paul DuBois, NewRiders 1999
Other PHP books (e.g. O’Reilly, WROX Press)
[email protected]
[email protected]