Web Database Programming Connecting Database to Web

Example Design Customers come to the web site and register. The sales department sets up a list of widgets that customers can order from. A customer makes one or more orders for widgets. When the order is filled the order is removed from the database. Widgets are classified by type.

SQL Query SELECT … FROM … WHERE … ORDER BY Examples of SQL –SELECT * FROM Customer –SELECT FirstName, LastName FROM Customer WHERE FirstName=“Andrew” AND LastName=“Fuller” –SELECT FirstName AS FName, LastName AS LName FROM Customer WHERE LastName=“Fuller” OR (YearOfBirth<"1950” AND Photograph Is Null) ORDER BY LastName

Get a Table and Display it on the Web Connect to a database server (get a handle to a connection) –Host –User name –Password Select a database Issue SQL query to get a table Fetch results row by row –Display each row Error checking in every step

Example Code Customer List <?php $db = mysql_connect(“db_host”, “db_user”,“db_pwd”) or die(“cannot connect”); mysql_select_db(“dbname”,$db) or die(“cannot select db”); $sql = “SELECT FirstName, LastName ”; $sql = $sql.“FROM Customer”; $result = mysql_query($sql,$db) or die(“query failed: ”.mysql_error()); while ($row = mysql_fetch_row($result)) { $fn = $row[“FirstName”]; $ln = $row[“LastName”]; print “ $fn $ln ”; } ?>

Include file Put database login information into a separate file –For Portability and security <?php $db_host = “localhost”; $db_user = “instruct”; $db_pwd = “xxxxx”; ?> Each database accessing script “include” this file at the beginning (or “require”) include(“db_login.php”); Use variables and functions in included file as if it is in this file

Using HTML Forms for Queries Example –For a customer table (FirstName, LastName) –Use a page to query the database, find a record, and display it –Later we will look at other actions you can take (insert, update, and delete) Notice –What happens when the user submits the form –Form display and form processing may be done with different files

The Form Display Part Tags in CustomerSimpleQueryForm.html Enter a first name: </form Notes –The form action is the URL of the file or script that will “handle” the form –The name of the form input field is used in the action file to identify the corresponding value, I.e. it is the same name in $_POST[‘name’]

The Action Query: $sql="SELECT FirstName, LastName from Customer "; $sql = $sql."WHERE FirstName='$_POST[queryFirstName]'"; $results = mysql_query($sql,$db) or die(“query failed: ”.mysql_error()); Notes –in SQL, enclose text in single quotes (‘text’) while numbers do not have them (e.g. 3 ) –The $sql string can be used for debugging (e.g. print(“sql = $sql”); )

The Output PhP Code Fragment while ($row = mysql_fetch_row($results)) { // print fields one by one // or use a loop print(" $row[0] $row[1] "); } Or: $count = mysql_num_rows($results); for ($i = 0; $i < $count; $i++) {… Note –what happens when result set is empty?

Redirect using header() The PHP function header() takes over the sending of the “header” to the client Example: if (!$_POST[queryFirstName]) { // there was no id value // so send the user to the add form header(“Location: add.html”); exit; // and get out of here! } Note there can be NO OUTPUT prior to the use of header() – no print statements – not even a blank line (outside of the <?php tag)

Alternate means of doing a Query URL parameters –On the URL following ?, and separated by & –Each value is a name=value pair –For example: yes These parameters can be accessed with $_GET[‘name’]