select
    d.dept_code as  DEPT_CODE
    ,DEPT_NAME
    ,ORDER_NO
    ,c.CUST_CODE as CUST_CODE
    ,CUST_NAME
    ,ORDER_AMT
from tbl_orders as o
inner join tbl_dept as d
on o.dept_code = d.dept_code
left outer join tbl_cust as c
on o.cust_code = c.cust_code
order by d.dept_code ,order_no