Duplicate entries from database - mysql

Question

ON closer inspection the problem is solved if I remove the comment table join, but obviously this isn't ideal help appreciated!!
I'm trying to write a blog with Codeigniter. At the moment i'm displaying all the information that I want to display, but for some reason, when viewing the blog, I've got duplicate content for the categories. There are only 3 test categories in my database but 1 of my test posts that has all 3 selected is showing six and the other is showing just the one category twice.
Even stranger than that, the first blog post is also counting the wrong number of comments. It's displaying 6 when there are only 4 in the database and only two are related to that post, but the strangest of all is that the second post displays the correct number of comments, two. How can that be.
This is the query from the model in question.
$this->db->select('posts.id,
posts.title,
posts.slug,
posts.content,
posts.author,
posts.date,
posts.time,
posts.tags,
posts.status,
GROUP_CONCAT(categories.name SEPARATOR \'-\') AS categories,
count(comments.id) as total_comments
');
$this->db->group_by(array('posts.id'));
$this->db->join('posts_categories', 'posts_categories.blog_entry_id = posts.id', 'left outer', 'left outer');
$this->db->join('categories', 'posts_categories.blog_category_id = categories.category_id', 'left outer');
$this->db->join('comments', 'comments.post_id = posts.id', 'left outer' );
$query = $this->db->get('posts', $config['per_page'], $this->uri->segment(3));
The standard query generated is this:
SELECT DISTINCT `posts`.`id`,
`posts`.`title`, `posts`.`slug`,
`posts`.`content`, `posts`.`author`,
`posts`.`date`, `posts`.`time`,
`posts`.`tags`, `posts`.`status`,
GROUP_CONCAT(categories.name SEPARATOR '-') AS categories,
count(comments.id) as total_comments
FROM (`posts`)
LEFT OUTER JOIN `posts_categories` ON `posts_categories`.`blog_entry_id` = `posts`.`id`
LEFT JOIN `categories` ON `posts_categories`.`blog_category_id` = `categories`.`category_id`
LEFT JOIN `comments` ON `comments`.`post_id` = `posts`.`id`
GROUP BY `posts`.`id` LIMIT 1
The database dump can be found here
Any help would be greatly appreciated, this is making me crazy!
Cheers.

Answer 1

Do you have any qualms running another query to get the comment count? You can do the following query (assuming Active Record):
$this->db->where('parent_id', $post_id);
$this->db->count_all_results('comments');
This would have to be run for each post, though, so your # of queries would be n+1 where n = number of posts.