Question

if I have three menus

id | name | order
--------------------
1  | Foo  | 1
2  | Bar  | 2
3  | Blah | 3

and click the link menu/up/1, I need to set order of menu with id 1 to 2 and menu with id 2 to 1.

I have tried (PDO)

public static function goDown($id) {
    if(!$id) {
        return false;
    }

    self::connect();
    self::prepare('SELECT count(*) FROM menu');
    $count = self::fetch();

    if(isset($count['count(*)'])) {
        self::prepare('UPDATE menu SET order = order - 1 WHERE order = :count');
        self::bindValue('count', $count['count(*)']);
        self::execute();

        self::prepare('UPDATE menu SET order = order + 1 WHERE id = :id AND order < :count');
        self::bindValue('id', $id);
        self::bindValue('count', $count['count(*)']);

        return self::execute();
    }
}

Thanks!

EDIT – MY SOLUTION:

public static function goDown($id) {
    if(!$id) {
        return false;
    }

    self::connect();
    self::prepare('SELECT count(*) FROM menu');
    $count = self::fetch();

    if(isset($count['count(*)'])) {
        self::prepare('SELECT ordem FROM menu WHERE id = :id LIMIT 1');
        self::bindValue('id', $id);
        $ordem = self::fetch();

        self::prepare('UPDATE menu SET ordem = ordem - 1 WHERE ordem = :ordem');
        self::bindValue('ordem', $ordem['ordem'] + 1);
        self::execute();

        self::prepare('UPDATE menu SET ordem = ordem + 1 WHERE id = :id AND ordem < :count');
        self::bindValue('id', $id);
        self::bindValue('count', $count['count(*)']);

        return self::execute();
    }
}

Answer 1

I don’t know how your table definition and keys are set up, but you will probably have to have an overlapping number for a split second. If that is ok, then do something like this:

The safest:

SELECT order FROM menu WHERE id = :id; /* One to go up; */
SELECT id, order FROM menu WHERE order = :existingOrder + 1; /* One to go down */

UPDATE menu SET order = order + 1 WHERE id = :id; /* Putting it up */
UPDATE menu SET order = :existingOrder WHERE id = :existingId

This uses an extra query, but is much safer. You can also validate that it isn’t at the top/bottom, too as that will cause problems.