将公式转换为SQL查询

Question

I am building a system where it would output the total current balance to the user.

I have a three MySQL tables, first a Members table where the user data session gets the Member_ID second is Regular_Savings and the third (The Out Put Table) Current_Balance

I have the Math formula how to work out the interest (see bellow)

I would like Total_Balance in Current_Balance table to use the output the current balance, I was trying to use the query bellow but think I have made a few mistakes.

Query And Codeigniter Model Code

function get_bank()
    {
        $this->db->SELECT(`Principle` * (POWER((1 + (`Annual_Rate_Interest` DIV `Compound`)),(`Valid_For` * `Compound`)))) +((`monthly_deposit` * (POWER((1 + (`Annual_Rate_Interest` DIV `Compound`)),(`Valid_for` * `Compound`)) -1)) DIV(`Annual_Rate_Interest` DIV `Compound`)) as fav, $this->session->userdata("Member_ID"));
        $query = $this->db->get('Regular_Savings');
        return $query->result();
    }

Formula

All help is very much appreciated, Thank You.

****************UPDATE********************

As suggested in a comment, I could use PHP, I the code bellow is close I think, but not right, any ideas ?

Possible PHP solution

<?php
function interest($Principle,$Compound,$Annual_Rate_Intrest,$Valid_For){
    $Accumulated=0;
    if ($Compound > 1){
            $Accumulated=interest($Principle,$Compound-1,$Annual_Rate_Intrest,$Valid_For);
            }
    $Accumulated += $Principle;
    $Accumulated = $Accumulated * pow(1 + $Annual_Rate_Intrest/(100 * $Valid_For),$Valid_For);
    return $Accumulated;
    }
?>

Answer 1

Using the shorthands outlined in your table, the calculation should be

// p : principal
// i : annual rate interest
// c: compound
// n : valid for
// R : monthly deposit

// calculate the terms that appear twice
$x = $i / $c;
$y = pow ( (1 + $x), ($n * $c) );

$vf = $p * $y + ( ($R * $y - 1 ) / $x );