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>
>
>
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