select
    d.dept_code
    ,d.dept_name
    ,o.order_no
    ,c.cust_code
    ,c.cust_name
    ,o.order_amt
from
    tbl_orders o
    left join tbl_cust c on o.cust_code = c.cust_code
    inner join tbl_dept d on o.dept_code = d.dept_code
order by
    d.dept_code, o.order_no
;