php – 在我的查询中添加另一个数据库连接会导致某些行无法看到

我正在尝试用codeigniter编写的博客查询问题.我已经设置了一个带有2个连接的查询用于帖子,它的分类使用了三个表：posts,categories和posts_categories现在我也想加入我的评论表,进行计数.

这是我模型中的代码,显示了我编写的通用帖子：

$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
                            ');
        $this->db->group_by(array('posts.id'));
        $this->db->from('posts');
        $this->db->join('posts_categories','posts_categories.blog_entry_id = posts.id');
        $this->db->join('categories','posts_categories.blog_category_id = categories.category_id');
        $query = $this->db->get();
        return $query->result_array();

这是结果：

(
[0] => Array
    (
        [id] => 1
        [title] => My first blog post!
        [slug] => my-first-blog-post
        [content] => This is my first blog post. Don't worry,it's just a test,my real blog won't be this boring,hopefully!
        [author] => Joni
        [date] => 2012-01-23
        [time] => 00:00:00
        [tags] => Testing
        [status] => 
        [categories] => Testing-More Tests-Test
    )

[1] => Array
    (
        [id] => 2
        [title] => This is another test-post
        [slug] => this-is-another-test-post
        [content] => Well you guessed it. another boring test post,enjoy!
        [author] => Joni
        [date] => 2012-01-23
        [time] => 00:00:00
        [tags] => Sexy
        [status] => 
        [categories] => Test
    )

)

现在,当我修改查询以实现第三次连接时,如下所示：

$this->db->select('posts.id,GROUP_CONCAT(categories.name SEPARATOR '-') AS categories,count(comments.id) as total_comments
                            ');
        $this->db->group_by(array('posts.id'));
        $this->db->from('posts');
        $this->db->join('posts_categories','posts_categories.blog_category_id = categories.category_id');
        $this->db->join('comments','comments.post_id = posts.id');
        $query = $this->db->get();
        return $query->result_array();

我最终得到了这个

(
[0] => Array
    (
        [id] => 1
        [title] => My first blog post!
        [slug] => my-first-blog-post
        [content] => This is my first blog post. Don't worry,hopefully!
        [author] => Joni
        [date] => 2012-01-23
        [time] => 00:00:00
        [tags] => Testing
        [status] => 
        [categories] => Testing-More Tests-Test
        [total_comments] => 3
    )

)

如果你已经做到这一点,抱歉这么久了,只是想提前说谢谢！

欢呼乔尼