在codeigniter中有多对多的数据库关联

Question

I am creating a sort of card collection programme with codeigniter and ion_auth for authentication. A user should be able to add a card to his collection. So i have a users table and a cards table and a junction/bridge table.

    users
    ID
    NAME

and

    cards
    ID
    NAME

and

    users_cards
    ID
    USER_ID
    CARD_ID

I want to accomplish a SELECT statement that retrieves the cards from a users through user_cards.

$this->db->select('*');
$this->db->from('cards');
$this->db->join('users_cards', 'users.id = users_cards.user_id', 'inner');
$this->db->join('users', 'users_cards.user_id = users.id', 'inner');
$query = $this->db->get();
return $query->result_array();

I cant seem to get a grasp at the concept of these joins. Can someone please help me?

Answer 1

Looks like the join statement is missing the reference to the 'cards' table.

$this->db->select('*');
$this->db->from('users_cards');
$this->db->join('users', 'users.id = users_cards.user_id', 'inner');
$this->db->join('cards', 'cards.id = users_cards.card_id', 'inner');
$query = $this->db->get();
return $query->result_array();

The idea is that you're trying to get a relationship going between users_cards and the other two tables by referencing their relevant ids