next and previous post link ordered alphabetically

Find the solution:
The hole snippet looks like this:

<?php
function filter_next_post_sort($sort) {
    global $post;
    if (get_post_type($post) == 'MyCustomPostType') {
        $sort = "ORDER BY p.post_title ASC LIMIT 1";
    }
    else{
        $sort = "ORDER BY p.post_date ASC LIMIT 1";
    }
    return $sort;
}
function filter_next_post_where($where) {
    global $post, $wpdb;
    if (get_post_type($post) == 'MyCustomPostType') {
        return $wpdb->prepare("WHERE p.post_title > '%s' AND p.post_type="". get_post_type($post)."" AND p.post_status="publish"",$post->post_title);
    }
    else{
        return $wpdb->prepare( "WHERE p.post_date > '%s' AND p.post_type="". get_post_type($post)."" AND p.post_status="publish"", $post->post_date);
    }
}

function filter_previous_post_sort($sort) {
    global $post;
    if (get_post_type($post) == 'MyCustomPostType') {
        $sort = "ORDER BY p.post_title DESC LIMIT 1";
    }
    else{
        $sort = "ORDER BY p.post_date DESC LIMIT 1";
    }
    return $sort;
}
function filter_previous_post_where($where) {
    global $post, $wpdb;
    if (get_post_type($post) == 'MyCustomPostType') {
        return $wpdb->prepare("WHERE p.post_title < '%s' AND p.post_type="". get_post_type($post)."" AND p.post_status="publish"",$post->post_title);
    }
    else{
        return $wpdb->prepare( "WHERE p.post_date < '%s' AND p.post_type="". get_post_type($post)."" AND p.post_status="publish"", $post->post_date);
    }
}

add_filter('get_next_post_sort',   'filter_next_post_sort');
add_filter('get_next_post_where',  'filter_next_post_where');

add_filter('get_previous_post_sort',  'filter_previous_post_sort');
add_filter('get_previous_post_where', 'filter_previous_post_where');