SELECT
    d.DEPT_CODE,
    d.DEPT_NAME,
    o.ORDER_NO,
    o.CUST_CODE,
    c.CUST_NAME,
    o.ORDER_AMT
FROM
    TBL_ORDERS o
INNER JOIN
    TBL_DEPT d ON o.DEPT_CODE = d.DEPT_CODE
LEFT JOIN
    TBL_CUST c ON o.CUST_CODE = c.CUST_CODE
ORDER BY
    d.DEPT_CODE ASC,
    o.ORDER_NO ASC;