Late update:
I've tried to write + in the binding panel as you said, but it doesn't help. It still only inserts the value from the column, and does not add it.
Here is the updated code:
$UpdateQuery->bindColumn("ProvningPlatserBokade", "i", "+".($WADABokning_update->getColumnVal("BokningAntal")) ."", "WA_DEFAULT");
Earlier:
The idea is that admin should be able to see how many places are booked for the specific activity. Each time a booking is made, the number of seats is added to the column associated with that activity.
The number 4 was just an example. Actually, it's a number that comes from another column in another table. So different from time to time. Here is the code from update server behavior:
<?php
if (isset($_POST["Update"]) || isset($_POST["Update_x"])) {
$UpdateQuery = new WA_MySQLi_Query($AboutBeer);
$UpdateQuery->Action = "update";
$UpdateQuery->Table = "Provning";
$UpdateQuery->bindColumn("ProvningPlatserBokade", "i", "".($WADABokning_update->getColumnVal("BokningAntal")) ."", "WA_DEFAULT");
$UpdateQuery->addFilter("ProvningID", "=", "i", "".($WADABokning_update->getColumnVal("ProvningID")) ."");
$UpdateQuery->execute();
$UpdateGoTo = "";
if (function_exists("rel2abs")) $UpdateGoTo = $UpdateGoTo?rel2abs($UpdateGoTo,dirname(__FILE__)):"";
$UpdateQuery->redirect($UpdateGoTo);
}
?>