sql命令无法正确执行

Question

I have a two tables in my database instructors and courses . I want to join them and for this reason wrote this code

$this->db->join('instructors', 'instructors.id = courses.instructor_id', 'left');
$query = $this->db->get_where('courses', array('courses_slug' => $slug));
return $query->row_array();

This code means:

SELECT * FROM `courses` LEFT JOIN `instructors` ON `instructors`.`id` = `courses`.`instructor_id` WHERE `courses_slug` = 'abituriyent-hazirligi'

But when I write this code to check:

$data['courses'] = $this->popular_courses_model->get_popular_courses($slug);
echo $data['courses']['id'];
die();

It writes the instructors id, not id of the course. Where can be the problem? Thanks in advance.

Answer 1

You are joining two table with columns of the same name ('id'). You need to be specific in your select for the columns and rename ('AS') if necessary.

select courses.id as course_id, instructor.id as instructor_id, ...

Answer 2

When using joins you should explicitly call out what columns you want returned like:

$select = "c.id, c.name, c.instructor_id, i.name instructor_name";

return $this->db->select($select)
//equivalent to "instructors as i" 
->join('instructors i', 'i.id = c.instructor_id', 'left')
->where('c.courses_slug', $slug)
//equivalent to "courses as c" 
->get('courses c')->row_array();