select  productID from your_table
   where meta_key = "_shop" and meta_value = "yes"

add_action('init',function(){
    global $wpdb;
    $ids = $wpdb->get_results("
                                SELECT p.ID as id 
                                From $wpdb->posts as p
                                LEFT JOIN $wpdb->postmeta as m
                                ON p.ID = m.post_id
                                WHERE m.meta_key = '_shop'
                                AND m.meta_value = 'yes'
                                AND p.post_type = 'product' OR p.post_type = 'product_variation'
                            ");
    if(!empty($ids)){
        foreach ($ids as $id) {
            echo $id->id;
        }
    }
});