Reducing sql value by one

[petenaylor]

Hi all

 

I have an SQL table with a quantity in and I am trying to write a piece of code to reduce the quantity by 1 each time. Here's my code:

 

$queryc = mysql_query(" SELECT FROM `voucher_codes` WHERE name = '".$voucherc."'");

$resultc = mysql_fetch_array ($queryc);

 

$voucherqtyvalue = $resultc['qty'];

 

$newvoucherqty = $voucherqtyvalue - 1;

 

$queryi = mysql_query(" UPDATE `voucher_codes` SET qty = '".$newvoucherqty."' WHERE name = '".$_SESSION['vouchercode']."'");

$resulti = mysql_result($queryi);

 

Instead, this changes the value to -1 in the table.

 

Please help!

 

Cheers

Pete

[laffin]

made much simpler with 1 query

UPDATE table SET qty=qty-1 WHERE name=vouchercode
[/code

[laffin]

wont keep it from going into negatives tho, just a thought

UPDATE table SET qty=qty-1 WHERE name=vouchercode AND qty>0

 

That should fix it

[petenaylor]

That's great any thanks!