如何在codeigniter 3中创建两个连接？

I have 3 Tables:

**Clients**
id | names 
1  | Paul
2  | Jack

**Course** 
id | names 
1  | Med 
2  | Nur 

**Class** 
class_id | clients_id  | course_id 
1        |   1         | 1
2        |   2         | 1
3        |   1         | 2 

**I want to show this:** 

**Result**
class_id |clients_names | courses_names
1        | Paul         | Med
2        | Jack         | Med 
3        | Paul         | Nur

How can i get this Result? I already know how to make one join, but this double join is driving me crazy.

Thks.

Try;

select 
    c.class_id, cl.names clients_names, co.names courses_names
from Class c
join Clients cl on cl.id = c.clients_id
join Course co on co.id = c.course_id 

You can simply use CI Active Records as

$this->db->select('cla.class_id,cli.names as clients_names, co.names as courses_names',false);
$this->db->from('Class cla');
$this->db->join("Clients cli","cla.clients_id = cli.id");
$this->db->join("Course co","cla.course_id = co.id");