Laravel Eloquent Sum of relation's column

You can use the sum method on an Eloquent relation to get the sum of a column's values.

Here's an example of how you can use it:

<?php

$users = App\User::with('orders')
    ->whereHas('orders', function ($query) {
        $query->where('status', 'completed');
    })
    ->get();

foreach ($users as $user) {
    $totalAmount = $user->orders->sum('amount');
}

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This will give you the sum of the amount column for all of the completed orders of each user.

Keep in mind that this will execute a separate query for each user to retrieve their orders, so it may not be very efficient if you have a large number of users. In that case, you may want to use a more efficient solution such as using a subquery or joining the tables.