How to make this query a little bit more readable?

If you are going to spread it out for readability, how about something like:

PHP Code:

return $this->db->from("reports AS a")
      ->select("a.id, 
            b.id AS employee_id, 
            {
                  CONCAT(      
                        b.last_name, 
                        ', ', 
                        b.first_name, 
                        ' ', 
                        b.middle_name
                  ) AS full_name
            }, 
            c.id AS machine_id, 
            c.title AS machine, 
            d.title AS hstatus, 
            a.created_on, 
            a.action_on, 
            a.edit_on, 
            a.problems_encountered, 
            a.corrective_action,
            a.root_caused,
            a.remarks,
            a.item_replaced"),
      ->join("employees AS b", "b.id = a.employee_id"),
      ->join("machines AS c", "c.id = a.machine_id"),
      ->join("hstatus AS d", "d.id = a.hstatus_id"),
      ->get()
      ->result_array(); 


You can chain the db calls which makes everything so much neater too.

I am not sure why you have all the AS statements. Personally my tables would have columns like machine_id and employee_id and every field in, say, the employee table starts with employee_first_name, employee_last_name etc. So no collisions, and much simpler queries, and I always know what table produced what field without any backtracking through queries. Personally I hate all the AS a and a.id = b.id or c.id as it is meaningless for a human reader.

I'll take a note at that.