PHP - 获取表中显示的值的总和

Question

I am using a pre defined php inventory manager. So in sales my data is getting stored this way:

[{"product_id":"8","total_number":"70","selling_price":"110"}]

To display these values in table I use the following code

$sub_total          =   0;
$invoice_entries    =   json_decode($row['invoice_entries']);
foreach ($invoice_entries as $row2):
    $sub_total  +=  ($row2->total_number * $row2->selling_price);                                       
endforeach;

$sub_total      =   $sub_total - ( $sub_total * ($row['discount_percentage'] / 100) );
$grand_total    =   $sub_total + ( $sub_total * ($row['vat_percentage'] / 100) );
echo $grand_total;

I get the desired output here which is the total value of the sale.

Now, I am trying to give a report feature which will show all the invoices with the client name, sale value. I want to calculate the total of all the invoices and show in a table row i.e. Total of $grand_total.

I am unable to understand how do I get that. Any java script could do it? I don't understand js well. So I have no clue if its possible with it or not.

Thanks in advance

Answer 1

since you storing data in database, you can use another query to sum up all the grand_total from all the record you want to retrieve.

select sum(grand_total) from yourTable where yourFilter

if grand_total is sum up from another query, you can use nested select statement to do it.

http://www.mysqltutorial.org/mysql-subquery/

this link have some example on nested select.