Joining two tables and query by meta key

Hi

Im using event calendar plugin where I can set event date for posts and it shows in calendar widget. Everything is working as inteded but I would also like to query post by event date (meta key start_datetime).

Problem is event date is stored in separate table named wp_ftcalendar_events so regular query will not work.

TABLE SCREENSHOT

I came up with this code (reading through codex etc.) Tried a lot of things but still can’t make it work (not a programmer :/) Would someone be kind enough to help?

<?php
global $wpdb;
global $post;
$date = date("Y-m-d");
$querystr = "
SELECT *
FROM wp_ftcalendar_events
JOIN wp_ftcalendar_events on posts.ID = wp_ftcalendar_events.post_parent
WHERE posts.ID = wp_ftcalendar_events.post_parent
AND $wpdb->posts.post_status = 'publish'
AND $wpdb->wp_ftcalendar_events.meta_key = 'start_datetime'
AND $wpdb->wp_ftcalendar_events.meta_value > " . $date . "
";

$pageposts = $wpdb->get_results($querystr, OBJECT); ?>
<?php if ($pageposts): ?>  

<?php global $post; ?>
<?php foreach ($pageposts as $post): ?>
<?php setup_postdata($post); ?>
<a href="<?php the_permalink() ?>"><?php the_title(); ?></a>
<?php endforeach; ?>
<?php endif; ?>