[php] How to INNER JOIN 3 tables using CodeIgniter

Can someone Tell me how to join 3 table with php? Example

SELECT FROM table1, table2,table on INNERJOIN -------------------

let I have 3 table.(question table ,answer table and category table) Here is example form my webpage.

Time remaining 30 minutes(I will get "30 minutes" form Category table)
1. Question (from question table)
2. answer (from answer table)

I don't know how to join 3 table.

$this->db->select('*');    
$this->db->from('table1');
$this->db->join('table2', 'table1.id = table2.id','JOIN Type');
$this->db->join('table3', 'table1.id = table3.id');
$query = $this->db->get();

this will give you result from table1,table2,table3 and you can use any type of join in the third variable of $this->db->join() function such as inner,left, right etc.

$this->db->select('*');    
$this->db->from('table1');
$this->db->join('table2', 'table1.id = table2.id', 'inner');
$this->db->join('table3', 'table1.id = table3.id', 'inner');
$this->db->where("table1", $id );
$query = $this->db->get();

Where you can specify which id should be viewed or select in specific table. You can also select which join portion either left, right, outer, inner, left outer, and right outer on the third parameter of join method.

function fetch_comments($ticket_id){
    $this->db->select('tbl_tickets_replies.comments, 
           tbl_users.username,tbl_roles.role_name');
    $this->db->where('tbl_tickets_replies.ticket_id',$ticket_id);
    $this->db->join('tbl_users','tbl_users.id = tbl_tickets_replies.user_id');
    $this->db->join('tbl_roles','tbl_roles.role_id=tbl_tickets_replies.role_id');
    return $this->db->get('tbl_tickets_replies');
}

I created a function to get an array with the values ??for the fields and to join. This goes in the model:

  public function GetDataWhereExtenseJoin($table,$fields,$data) {
    //pega os campos passados para o select
    foreach($fields as $coll => $value){
        $this->db->select($value);
    }
    //pega a tabela
    $this->db->from($table);
    //pega os campos do join
    foreach($data as $coll => $value){
        $this->db->join($coll, $value);
    }
    //obtem os valores
    $query = $this->db->get();
    //retorna o resultado
    return $query->result();

}

This goes in the controller:

$data_field = array(
        'NameProduct' => 'product.IdProduct',
        'IdProduct' => 'product.NameProduct',
        'NameCategory' => 'category.NameCategory',
        'IdCategory' => 'category.IdCategory'
        );
    $data_join = array
                    ( 'product' => 'product_category.IdProduct = product.IdProduct',
                      'category' => 'product_category.IdCategory = category.IdCategory',
                      'product' => 'product_category.IdProduct = product.IdProduct'
                    );
    $product_category = $this->mmain->GetDataWhereExtenseJoin('product_category', $data_field, $data_join);

result:

echo '<pre>';
    print_r($product_category);
    die;

you can modiv your coding like this

 $this->db->select('a.nik,b.nama,a.inv,c.cekin,c.cekout,a.tunai,a.nontunai,a.id');
 $this->db->select('DATEDIFF (c.cekout, c.cekin) as lama');
 $this->db->select('(DATEDIFF (c.cekout, c.cekin)*c.total) as tagihan');
 $this->db->from('bayar as a');
 $this->db->join('pelanggan as b', 'a.nik = b.nik');
 $this->db->join('pesankamar_h as c', 'a.inv = c.id');
 $this->db->where('a.user_id',$id);
 $query = $this->db->get();
 return $query->result();

i hope can be resolve your SQL

I think in CodeIgniter the best to use ActiveRecord as wrote above. One more thing: you can use method chaining in AR:

$this->db->select('*')->from('table1')->join('table2','table1.id=table2.id')->...

For executing pure SQL statements (I Don't Know About the FRAMEWORK- CodeIGNITER!!!) you can use SUB QUERY! The Syntax Would be as follows

SELECT t1.id FROM example t1 INNER JOIN (select id from (example2 t1 join example3 t2 on t1.id = t2.id)) as t2 ON t1.id = t2.id;

Hope you Get My Point!

I believe that using CodeIgniters active record framework that you would just use two join statements one after the other.
eg:

$this->db->select('*');
$this->db->from('table1');
$this->db->join('table1', 'table1.id = table2.id');
$this->db->join('table1', 'table1.id = table3.id');
$query = $this->db->get();

Give that a try and see how it goes.