How to sum the values of grouped sum values | PHP mySQL

Question

The following PHP script joins two tables together and displays JSON based on the query.

<?php

$con=mysqli_connect("localhost","username","password","dbName");


if (mysqli_connect_errno())
{
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
}


$sql =  "SELECT User, SUM(Price) as sumValue 
FROM Table1
LEFT JOIN Table2 USING(Product)
GROUP BY User";

if ($result = mysqli_query($con, $sql))
{

    $resultArray = array();
    $tempArray = array();

    while($row = $result->fetch_object())
    {
        $tempArray = $row;
        array_push($resultArray, $tempArray);
    }

    echo json_encode($resultArray);
}

mysqli_close($con);


?>

Because the query groups by the user, each user shows its own sumValue.

And I get the following JSON results:

[{"user":"Jack","sumValue":"4.50"},
{"user":"Jake","sumValue":" 4.00 "},{"user":"Mary","sumValue":" 8.50 "}] 

How can I add a sum of all the sumValue and display them at the end of the JSON like:

[{"user":"Jack","sumValue":"4.50"},
{"user":"Jake","sumValue":" 4.00 "},{"user":"Mary","sumValue":" 8.50 "}, 
{"sumTotal": "17.00"}]

Answer 1

Untested but I think you can make one more variable, add to it in the loop, then append after the execution and before the json creation.

$tempArray = array();
$sum = 0;
while($row = $result->fetch_object())
{
    $tempArray = $row;
    array_push($resultArray, $tempArray);
    $sum += $tempArray['sumValue'];
}
array_push($resultArray, array('sumTotal' => $sum); 
echo json_encode($resultArray);

Answer 2

Simply sum them in the loop.

<?php
$con=mysqli_connect("localhost","username","password","dbName");


if (mysqli_connect_errno())
{
  echo "Failed to connect to MySQL: " . mysqli_connect_error();
}


$sql =  "SELECT User, SUM(Price) as      sumValue 
FROM Table1
LEFT JOIN Table2 USING(Product)
GROUP BY User";

if ($result = mysqli_query($con, $sql))
{

    $resultArray = array();
    $tempArray = array();

    // you want an array of objects, so create an object to sum the sub totals
    $total = new stdClass;
    $total->sumTotal = 0;

    while($row = $result->fetch_object())
    {
        $tempArray = $row;
        array_push($resultArray, $tempArray);

        // $resultArray[] = $row;  // shorter... $tempArray unneeded.

        $total->sumTotal += $row->sumValue;

        // better way to do it:
        // $total->sumTotal = bcadd($total->sumTotal, $row->sumValue);
    }

    $resultArray[] = $total;
    echo json_encode($resultArray);
}

mysqli_close($con);


?>

However, there is one huge caveat: floating point math.

If precision is important, such as in currency, you'll want to use bcmath function

Answer 3

Try this:

if ($result = mysqli_query($con, $sql))
    {
        $resultArray = array();
        $total = 0;

        while($row = $result->fetch_object())
        {
            array_push($resultArray, $row);
            $total += $row->sumValue;
        }

        array_push($resultArray, array('sumTotal' => $total));
        echo json_encode($resultArray);
    }