RE: [PHP] Re: PHP and mySQL
| From: | John Holmes | Date: | Tue, 14 May 2002 01:06:41 +0000 |
| Subject: | RE: [PHP] Re: PHP and mySQL | ||
| References: | 1 | Groups: | php.general |
| Request: | Send a blank email to php-general+get-97444@lists.php.net to get a copy of this message | ||
Why can't you use one query?
UPDATE Book2 SET stock = stock - $quantity WHERE stock >= $quantity AND
booktitle = '$booktitle'
---John Holmes...
> -----Original Message-----
> From: Matthew Ward [mailto:email@inspirationstudios.co.uk]
> Sent: Monday, May 13, 2002 11:52 AM
> To: php-general@lists.php.net
> Subject: [PHP] Re: PHP and mySQL
>
> 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" <sullivan@ccc-e.net> wrote in
> message
> news:OIBBKNAFKLNGCMHCDGIKCEGBCDAA.sullivan@ccc-e.net...
> > 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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