php sql problem
Posted by phillipmulvaney (phillipmulvaney), 29 April 2004hi,
I am having trouble with some simple maths here.
I want to retrieve "quantity" from table "a" subtract 1 from the "quantity" and then post this new "quantity" back to the database.
I can retrieve the "quantity" but when I subtract 1 from it nothing happens.
Here is the code:
$table_name = "a";
$sql = "SELECT quantity FROM $table_name
WHERE barcode = '$_POST[barcode]'";
$result = @mysql_query($sql,$connection)
$num = mysql_num_rows($result);
$sum = 0;
// want to take 1 from quantity
$sum = quantity --;
quantity = $sum;
//now want to post the new quantity
// back to the database
$sql = "update a set quantity
where barcode = '$_POST[barcode]'";
Posted by admin (Graham Ellis), 29 April 2004Answer linked (somewhat) to your other post.
You've carefully written an sql command into the $sql variable, but you haven't run mysql_query on the variable to send it across to the MySQL daemon
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