PHP - Calculate running balance [duplicate] - php

Question

This question already has an answer here:
How Can Calculate Credits,Debits & Balance in the general ledger?
(1 answer)
Closed last year.
I am trying code in php with mysql and I want to calculate running balance based on the type of transaction. My database table is as per below
id | amt | type | date
----+---------+----------+-----------
1 | 70000 | Cr | 01-01-2022
2 | 8000 | Dr | 01-01-2022
3 | 60000 | Cr | 02-01-2022
4 | 50000 | Dr | 02-01-2022
5 | 90000 | Cr | 03-01-2022
6 | 28000 | Dr | 03-01-2022
And I want the result as per below, if type = Cr then ADD and if type = Dr then SUBTRACT and auto calcuate running BALANCE where initial value to be ZERO
id | Dr | Cr | date | balance
----+----------+---------+-------------+----------
1 | 0 | 70000 | 01-01-2022 | 70000
2 | 8000 | 0 | 01-01-2022 | 62000
3 | 0 | 60000 | 02-01-2022 | 122000
4 | 50000 | 0 | 02-01-2022 | 72000
5 | 0 | 90000 | 03-01-2022 | 162000
6 | 28000 | 0 | 03-01-2022 | 134000
The following is the PHP script I'm currently using
<table>
<tr><th>Date</th><th>IN</th><th>OUT</th><th>Balance</th></tr>
<?php
$conn=mysqli_connect("details hidden");
$sql="SELECT * FROM table_name WHERE type IN ('Dr', 'Cr') ORDER BY date DESC";
$query=mysqli_query($conn, $sql);
while ($row=mysqli_fetch_array($query)) {
echo '<tr>';
echo '<td>'.$newdate = date('d-m-y', strtotime($row['date'])).'</td>';
if ($row['type']==Dr){
echo '<td>'.$row['amt'].'</td>';
echo '<td></td>';}
elseif ($row['type']==Cr){
echo '<td></td>';
echo '<td>'.$row['amt'].'</td>';}
else {
echo '<td></td>;
echo '<td></td>;}
echo '</tr>';
}
?>
</table>
Any help would be helpful.

Answer 1

You can use the sum window function to get the result you want:
select id,
case when `type` = 'Dr' then `amt` else 0 end as Dr,
case when `type` = 'Cr' then `amt` else 0 end as Cr,
date,
sum(case when `type` = 'Dr' then -`amt` when `type` = 'Cr' then `amt` end) over(order by date rows unbounded preceding) as balance
from table_name;
Fiddle