How to insert calculated field into database?

Question

I am inserting multiple records into a database. Many of the fields are consistent, but one field is calculated, and needs to calculate/subtract the value for each record inserted into the database.

<?php
$ExecuteQuery = new WA_MySQLi_Query($numeroseti);
$ExecuteQuery->Statement = "INSERT INTO transactions 
(fromAcct, amount, fromAcctNewBalance, toAcctNewBalance, toAcct, description, timestamp) 
(SELECT 1, ?, ?, balance + ?, acct_number, 'issuance', $time FROM users WHERE acct_number NOT LIKE '1800%' AND type <> 1 AND user_active = 1)";
$ExecuteQuery->bindParam("d", "".($_POST['issue_balance'])  ."", "0"); //acct1num
$ExecuteQuery->bindParam("i", "".($getSender->getColumnVal("balance") - $amount)  ."", "-1");
//acct2num
$ExecuteQuery->bindParam("i", "".($amount)  ."", "-1");
//acct3num
$ExecuteQuery->execute();
?>

The field is fromAcctNewBalance that I am having issues with. This is the code that calculates (like a ledger) what the new balance is:

$getSender->getColumnVal("balance") - $amount;

The problem is, it puts the same value into each record, when it should be subtracting the amount each time a new record is added.

For example, if the fromAcctNewBalance starting balance is 600 and the amount issued to a user is 10, and next record that is added should have a fromAcctNewBalance of 590, and so on, until it runs out of records to add to the table.

Does anyone have any ideas on how I can fix this issue?

Answer 1

I think the mistakes lies in the use of -> inside the bindParam .

So I tried to do the substraction without the bindParam and $getSender->$getColumnVal - $amount; simply doesn't work.

Use it like this

$getSender = $getColumnVal("balance") - $amount;
$ExecuteQuery->bindParam("i", "".($getSender)  ."", "-1");

" -> , is used when you want to call a method on an instance or access an instance property."

It is unclear to me, if your $getColumnVal("balance") is a method or instance. If it is so, use it like this:

$getSender -> $getColumnVal("balance");
$getSender = $getSender - $amount;
$ExecuteQuery->bindParam("i", "".($getSender)  ."", "-1");

References:

Where do we use the object operator "->" in PHP?

https://www.php.net/manual/de/language.types.object.php

EDIT:

Full code example

<?php
$ExecuteQuery = new WA_MySQLi_Query($numeroseti);
$ExecuteQuery->Statement = "INSERT INTO transactions 
(fromAcct, amount, fromAcctNewBalance, toAcctNewBalance, toAcct, description, timestamp) 
(SELECT 1, ?, ?, balance + ?, acct_number, 'issuance', $time FROM users WHERE acct_number NOT LIKE '1800%' AND type <> 1 AND user_active = 1)";
$ExecuteQuery->bindParam("d", "".($_POST['issue_balance'])  ."", "0"); //acct1num

//Use the one that fits best
    $getSender = $getColumnVal("balance") - $amount;
    $ExecuteQuery->bindParam("i", "".($getSender)  ."", "-1");

//or 
    $getSender -> $getColumnVal("balance");
    $getSender = $getSender - $amount;
    $ExecuteQuery->bindParam("i", "".($getSender)  ."", "-1");

//acct2num
$ExecuteQuery->bindParam("i", "".($amount)  ."", "-1");
//acct3num
$ExecuteQuery->execute();
?>

Answer 2

This ended up working for me:

    while (!$getRecipients->atEnd())
{
    $ExecuteQuery = new WA_MySQLi_Query($numeroseti);
    $ExecuteQuery->Statement = "INSERT INTO transactions 
     (fromAcct, amount, fromAcctNewBalance, toAcctNewBalance, toAcct, description, timestamp) 
    VALUES (1, ?, ?, ?, ?, 'issuance', $time)";                 
    $ExecuteQuery->bindParam("i", "".($amount)  ."", "0");
    $ExecuteQuery->bindParam("i", "".($startingbalance)   ."", "-1");   
    $ExecuteQuery->bindParam("i", "".($amount)  ."", "-1");
    $ExecuteQuery->bindParam("i", "".($getRecipients->getColumnVal("acct_number"))  ."", "-1");
    $ExecuteQuery->execute();
    
    $startingbalance = $startingbalance - $amount;
    $getRecipients->moveNext();
}
$getRecipients->moveFirst();