How to get all custom fields values from ALL posts

Each post have 2 custom fields:
key_1 = value_1
key_2 = value_2
How to get all these custom fields values from ALL posts that have post_status = ‘publish’?

I try something like that:

global $post;
global $wpdb;
$sql = "SELECT * FROM $wpdb->postmeta
				LEFT JOIN $wpdb->postmeta ON ($wpdb->posts.post_status = $wpdb->postmeta.post_status)
				WHERE meta_key = 'key_1' OR meta_key = 'key_2'
				AND post_status = 'publish'
				ORDER BY post_id ASC";

$custom_fields = $wpdb->get_results($sql);

echo '<pre>';
print_r ($custom_fields);
echo '</pre>';

But it didn’t work. Just an ampty arrow. Can anybody help?