Data-Driven Web Pages Stephen Rondeau 18 May 2009

Agenda Problem Statement Static vs. Dynamic Information Browsers and Web Servers Quick Database Tutorial Web and Database Servers How to Access a Database from Web Page

Problem Statement “Put x on the web” x could be employee data, songs, order info, etc. Questions to ask: Why? What information – all or partial? What can be done? Who can do what?

Sample Data In File

Static vs. Dynamic Information Could put information directly in web pagedirectly in web page Can be formatted to look better Someone who knows about web pages can update Okay solution if data doesn't change more than once per day and entire information is desired Could put information into a file that page referencesfile that page references Link to a text file Anyone could update – no knowledge of web Easier to maintain, but doesn't look great Information is static cannot be changed except by updating entire file What if person who updates can't do it?

Web Page with Data 101 John Smith 102 Jane Doe 103 Mary Adams 104 Tim O'Brian

Static vs. Dynamic Information Dynamic information: data can change often Web page displays a snapshot of current data Someone is adding, changing or deleting data If new or changed data comes from the web, how does it get there from browser?

Browsers and Web Servers Web Server Browser

Browsers and Web Servers Web Server Browser GET index.html

Browsers and Web Servers Web Server Browser index.html

Browsers and Web Servers Web Server Browser Last Name: First Name: <input type="submit" name="submit" value="Submit"> See form form.html lu.php form.html GET form.html form.html

Browsers and Web Servers Web Server Browser POST lu.php?ln=Smith&fn=Joe Last Name: First Name: <input type="submit" name="submit" value="Submit"> See form form.html lu.php lname= fname=<?php echo $_POST["fn"]; ? form.html lu.php HTML from lu.php

Quick Database Tutorial Evolved from simple files  programs supporting searching files for criteria needed to be changed for each new set of data  updating and deleting was difficult and inefficient Generalized, consistent way to structure data Data is efficiently stored and can be searched Database is collection of tables and other info table consists of rows of related columns of data  each column is named and typed other info includes user accounts and passwords, views, indices, procedures, etc.

Sample Data in Table

Quick Database Tutorial Data usually accessed via SQL SQL is Structured Query Language  INSERT puts data in table  SELECT retrieves data that matches criteria  UPDATE changes data in table  DELETE removes data from table Examples insert into employees(id, firstname, lastname) values(105,'Lee','O''Leary') select * from employees where lastname='Smith'

Quick Database Tutorial DBMS: Database Management System Common DBMSes:  Oracle, IBM DB2, Microsoft SQL Server Robust, heavy-duty, complex, large, server-based, expensive  MySQL, Firebird Robust, medium-duty, understandable, small, server-based, free  Microsoft Access Adequate, light-duty, very understandable, medium, local, affordable De-emphasizes SQL, but it's there Simple export to SQL Server

Web and Database Servers Browser Web Server Database Server OR Browser Web and Database Server

How to Access DB from Web Use PHP and ODBC PHP: Perl Hypertext Processor  Scripting language for dynamic web pages  Embedded in HTML:  Must be installed and configured on web server ODBC: Open DataBase Connectivity  Standardized way to access DBMSes  Independent of programming language, DBMS, OS  Can switch to different DBMSes without changing code

How to Access DB from Web PHP ODBC functions: must be installed  odbc_connect(): connect to DB  odbc_exec(): execute SQL statement  odbc_fetch_row(): get a returned row from odbc_exec()  odbc_result(): pick out column data from row  odbc_close(): cleanup and close DB connection

How to Access DB from Web Outline of tasks: Connect to DB and save connection “handle”  Use odbc_connect() Do something with DB via connection handle  Pass a SQL statement to odbc_exec()  Usually loop over returned rows with odbc_fetch_row() Extract data from rows using odbc_result() Close DB connection  Use odbc_close()

Connecting to Database Using “housing” database Access database exported to SQL Server Will use tblEmployees Save as file "connect_db.php": <?php $db = odbc_connect("dsn", "user", "pw") or die "not connected"; print "connected "; ?> – _test.php _test.php dsn is reference to database or "data set name" user is database user id; pw is password for that user id

Displaying a Table Copy "connect_db.php" to "show.php" In place of print line: $stmt = "select * from tblEmployees"; $result = odbc_exec($db, $stmt); if ($result == FALSE) die("Problem with $stmt"); while (odbc_fetch_row($result)) { print odbc_result($result, "LastName"). ", ". odbc_result($result, "FirstName"); print " "; }

Searching a Table Search table for last name Last name is supplied by user via browser Two part process: Part 1: accept search "key" from the user Part 2: perform the search using the key Part 1: Asking the user is HTML save as "get_key.php" Last Name:

Searching a Table, Part 2 For example, let's say the key value is 'Smith' Part 2: performing the search is PHP Any user information in $_POST[ ]  e.g., $_POST[“key”]  Value is Smith Copy "show.php" to "search.php" and modify as follows $key = str_replace("'", "''", $_POST["key"]); $stmt = "select * from tblEmployees where LastName = '$key'"; First line gets key passed from "get_key.php", replacing each single quote with two single quotes Second line uses SQL to search table for match

Adding/Changing/Deleting Table Contents Standard form (table display): Add a record Change/Delete record 1… Change/Delete record 2… Change/Delete record 3… etc. "Add a record" is a link to add.php, which asks user for field values of record "Change" is a link to change.php with the record id supplied "Delete" is a link to del.php with the record id supplied

HTML for Add/Change/Delete HTML: Add a record Change / Delete … add.php doesn't require an id: new record change.php and del.php pass the id value in the query string; here the id is 24, e.g.

Add Process Like searching, two parts: Part 1: get values from user for fields of record Part 2: insert the record in the table with id add.php: Last Name: First Name:

Add Process, Part 2 add_rec.php (just the important pieces): $lastname = str_replace("'","''",$_POST["lastname"]); $firstname = str_replace("'","''",$_POST["firstname"]); $stmt = "select max(employeenumber)+1 from tblEmployees"; $result = odbc_exec($db, $stmt); $new_id = odbc_result($result, 1); $stmt = "insert into tblEmployees(employeenumber, lastname, firstname) values($new_id, '$lastname', '$firstname')"; $result = odbc_exec($db, $stmt); if ($result == FALSE) die("Could not insert $stmt");

Change Process Three parts: Part 1: get values from table Part 2: let user change field values of record Part 3: update the record using id and other values

Change Process, Part 1 change.php (first part): <?php include 'connect_db.php'; $id = $_GET["id"]; $stmt = "select * from tblEmployees where employeenumber=$id"; $result = odbc_exec($db, $stmt); if ($result == FALSE) die("Could not find $id: $stmt"); $lastname = odbc_result($result, "LastName"); $firstname = odbc_result($result, "FirstName"); odbc_close($db); ?>

Change Process, Part 2 change.php (second part): <input type="hidden" name="id" value=" "> Last Name: <input type="text" name="lastname" value=" "> First Name: <input type="text" name="firstname" value=" ">

Change Process, Part 3 change_rec.php (just the important pieces): $id = $_POST["id"]; $lastname = str_replace("'", "''", $_POST["lastname"]); $firstname = str_replace("'", "''", $_POST["firstname"]); $stmt = "update tblEmployees set lastname='$lastname', firstname='$firstname' where employeenumber=$id"; $result = odbc_exec($db, $stmt); if ($result == FALSE) die("Could not update: $stmt");

Delete Process Could be simple – delete immediately via del.php (just the important pieces): $id = $_GET["id"]; $stmt = "delete from tblEmployees where employeenumber=$id"; $result = odbc_exec($db, $stmt); But deleting immediately doesn't allow for user mistake – should confirm with the user  search for info associated with id (e.g., lastname and firstname)  display info to user and ask for permission to delete, then delete as above if okay  how to do the confirmation is left as an exercise for the reader

References Documentation (includes PHP source) Web Page Examples