Someone help me with this wpdb-> sql statement?

I’m trying to echo the results of a field that displays every row that the current post’s category has in common with.

<?php

<!--grabs the current post's categorie's id-->

$thiscat = $wpdb->get_var($wpdb->prepare("
   SELECT term_relationships.term_taxonomy_id
   FROM  $wpdb->posts
   LEFT JOIN $wpdb->term_relationships
      on $wpdb->posts.id = $wpdb->term_relationships.object_id
   WHERE $wpdb->posts = post->id"));

<!--grabs all the rows that has a category id that matches $thiscat-->

$episodelist = $wpdb->get_results("
   SELECT post_episode
   FROM $wpdb->posts
   LEFT JOIN $wpdb->term_relationships
      on $wpdb->post.post_id = $wpdb->term_relationships.object_id
   LEFT JOIN $wpdb->terms
      on $wpdb->term_relationships.term_taxonomy_id  = $wpdb->terms.term_id
   WHERE $wpdb->terms.name = $thiscat ");

<!--print the results-->	

foreach ($episodelist as $episodelist) {
echo $episodelist->post_episode; }

?>

I get no result.