SUM php/mysql multi-tables

Question

I would like to display the sums of the numbers in the columns of different tables. Tables are governed by a database join. I do not find the correct syntax to display the sums separately, it calculates everything without differentiating the arrays. Currently I have this:

$reqSomme = $db->query("SELECT SUM(prix) AS somme FROM PulseTasks JOIN PulseTables ON PulseTasks.id_table = PulseTables.id_table");
$reqSomme->execute();
$sum = $reqSomme->fetch(PDO::FETCH_ASSOC);

and

<td><?= $sum['somme'] ?> €</td>

It gives me visually this, it may speak to you more: