MySql 在 codeigniter 中使用两个不同的 join 语句联接两个表

Question

下面的连接在MySQL中是否有效

$this->db->select('A.plan_prepared_by,A.approval_date, U.display_name');
$this->db->from('A');
$this->db->where('plan_id', $planid );
$this->db->join('U','U.id=A.approval_user_id','left');
$this->db->join('U','U.username =A.plan_prepared_by','left');

Answer 1

您可以通过输入别名来尝试这样的操作

$select =   array(
                    'A.plan_prepared_by',
                    'A.approval_date',
                    'UL.display_name'
);
$where  =   array(
                    'plan_id'   =>  $planid
);

$this->db->select($select);
$this->db->from('A');
$this->db->where($where);
$this->db->join('U AS UL','UL.id = A.approval_user_id','left');
$this->db->join('U AS UR','UR.username = A.plan_prepared_by','left');