To delete the WordPress post revisions you only need one SQL statement. Execute this SQL query to remove all post revisions from your MySQL database:
DELETE a, b, c
FROM `wp_posts` a
LEFT JOIN `wp_term_relationships` b ON a.id = b.object_id
LEFT JOIN `wp_postmeta` c ON a.id = c.post_id
LEFT JOIN `wp_term_taxonomy` d
ON b.term_taxonomy_id = d.term_taxonomy_id
WHERE a.post_type = “revision”
AND d.taxonomy != “link_category”;
DELETE from `wp_posts` WHERE post_type=”revision”;