loop parent record followed by children, parent and children etc

I have seen a few questions like this and variations of this but I am still confused as how to go about doing this. I have different dealers in different regions and want to list them by region in one long list.

West Coast
dealer 1
dealer 2
dealer 3

East Coast
dealer 1
dealer 2
dealer 3

And so on...

I have a database table with a list of regions and another table with a list of dealers.

The dealer table has a column which contains the region id from the regions table so I can join the tables.

I tried this:

$stmt = $link->prepare("SELECT `region_name`, `dealer_name` FROM `dealer_region` as `dr` INNER JOIN `dealers` as `d` ON dr.`id` = d.`region_id` GROUP BY `region_name`");
$stmt->execute();
$result = $stmt->get_result();
$numRows = $result->num_rows;
if($numRows > 0) {
    while($row = $result->fetch_assoc()) {
        $dealer_name = $row['dealer_name'];
        $region_name = $row['region_name'];
        echo $region_name . "<br />" . $dealer_name . "<br />";
    }
}

$stmt->close();

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But this only results in one dealer being shown under each region instead of all.