PHP Mysql更新产品库存/数量

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Hello. I'm having a hard time with this. What i'm to do is discount the stock of certain product every time that a new entry is created (MYSql INSERT). So, the idea is INSERT the entry then UPDATE the Stock/Qty of the product that was sold.

Table Entrys for INSERT Table products UPDATE (idprod, stock, description)

This is my Qty input

<input type="text" name="txtQty<?=$i;?>" id="txtQty<?=$i;?>" value="1" size="3">

This is my MYSql Sentence after the INSERT

$sql_Qty = "UPDATE products SET stock = stock - '".$_POST['txtQty$i']."' WHERE idprod = '".$_POST['txtidp$i']."'";
$objQueryQty = mysql_query($sql_Qty);

Thanks!

Your UPDATE query should be this:

$sql_Qty = "UPDATE products SET `stock` = 'stock-".$_POST['txtQty'.$i]."' WHERE `idprod` = '".$_POST['txtidp'.$i]."'";

Solved! Just a very little fix in the Broken Heart Sentence.

$sql_Qty = "UPDATE products SET `stock` = stock-'".$_POST['txtQty'.$i]."' WHERE `idprod` = '".$_POST['txtidp'.$i]."'";