I presume that "quantity" is the number of books that the person has ordered, and therefore it needs to be a variable (ie with a $ infront of it) and its also best to do the calculation outside of the SQL statement just to be sure it works, eg:
if ($submit){ if(isset($booktitle) && isset($quantity)){ $retrievestock = mysql_query("SELECT stock FROM Book2 WHERE booktitle = '$booktitle'"); while($getstock = mysql_fetch_array($retrievestock)) { $stockamount = $getstock[stock]; } $newamount = $stockamount - $quantity; $sql = mysql_query("UPDATE Book2 SET stock = '$newamount' WHERE booktitle= '$booktitle'"); if(! $sql) { print("Could not update stock amount."); } elseif(! $submit) { print("Your order has not been placed.<p>"); } "City Colleges Of Chicago - Mannheim" <[EMAIL PROTECTED]> wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > I am a student working on a practicum problem. I have a mySQL database that > contains the books, their title, and how many are in stock. When a person > orders one of the books, I want the stock to be adjusted by how many, > quantity, that they chose when the submit button is clicked. The scripts > are written in PHP. > Here is part of my code: > <P>The book you are ordering: > > <? > echo " $booktitle "; > ?> > > <P>Additional Message:<br> > <textarea name="message" cols=30 rows=3></textarea> > </p> > <INPUT type="submit" value="Send your order."> > <input type=hidden name="booktitle" value="<? print $booktitle; ?>"> > </FORM> > > <?php > $user = "adminer"; > $pass = "hoosiers"; > $db = "Book Store1"; > $local = "jolinux"; > $link = mysql_connect( "$local", $user, $pass ); > if (! $link ) > die ( "Couldn't open the database" ); > mysql_select_db( $db, $link ) > or die ( "Couldn't open the $db: ".mysql_error() ); > > if ($submit){ > if( $booktitle, 'quantity' ){ > $sql = "UPDATE Book2 SET stock ='$stock-quantity' WHERE booktitle=$booktitle > AND quantity=quantity"; > } > // $result = mysql_query($mysql); > }else if(!$submit){ > echo "Your order has not been placed.<p>"; > } > ?> > </BODY> > </HTML> > > -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php