Codeigniter MySQL JOIN查询

Question

Im a beginner in MySQL, I got a hard time joining 2 tables in Codeigniter. So let me explain my tables.

In the first table named forum_topic I got these columns

topic_id topic_sk topic_subject topic_desc posted_by date_posted
1 123Qwe Rules and Regulations Anything Jonas Dulay 2015-11-03 11:15 PM

The second table is named forum_comment
comment_id topic_sk
1 123Qwe
2 123Qwe

The expected result will be like this
Topics Replies Date Posted by
Rules and Regulation 2 2015-11-03 11:15 PM Jonas Dulay

I dont know the process of getting the count of number of comment in other table
then join it . This is my query but it seems it will not help you.

    $this->db->select('*,count(forum_comment.topic_sk) as count');
    $this->db->from('forum_topic');
    $this->db->where(array('f_cat_id'=>$cat,'topic_status'=>1))
    ->join('forum_comment','forum_comment.topic_sk = forum_topic.topic_sk','left')
    ->group_by('forum_topic.topic_sk');

    $this->db->order_by('pinned',"DESC");
    $this->db->order_by("date_posted","DESC");

    $query= $this->db->get();
    return $query->result();

Answer 1

Please try below query, I think this is useful for you:

$this->db->select('ft.*,', FALSE);
 $this->db->select('IFNULL(COUNT(fc.topic_sk),0) as count', FALSE);
 $this->db->from('forum_topic as ft');
 $this->db->join("forum_comment as fc", ' rc.topic_sk = ft.topic_sk','left');
 $this->db->group_by('ft.topic_sk');
 $this->db->order_by('pinned',"DESC");
 $this->db->order_by("date_posted","DESC");

 $query= $this->db->get();
 return $query->result();