這篇 T-SQL 多筆金額統計 顯示方法
http://ithelp.ithome.com.tw/question/10180955?tag=hp.all
匿名發問的, 鑒於以往匿名發問者時常刪除,
造成後續參考的困擾.
所以還是用分享的方式.

On Oracle
CREATE TABLE ithelp160202a(
firm CHAR(1) NOT NULL,
part CHAR(3) NOT NULL,
price INTEGER NOT NULL
);

INSERT ALL
INTO ithelp160202a VALUES('A', '123', 100)
INTO ithelp160202a VALUES('A', '456', 200)
INTO ithelp160202a VALUES('B', '789', 300)
SELECT 1
  FROM DUAL;
  
COMMIT;

SELECT firm
     , a.part
     , a.Price
     , CASE
        WHEN a.RowN = 1 THEN b.TotPri
        ELSE NULL
       END TotPri
  FROM (SELECT firm
             , part
             , SUM(price) OVER(PARTITION BY firm, part, price) Price
             , ROW_NUMBER() OVER(PARTITION BY firm ORDER BY part) RowN
         FROM ithelp160202a
        GROUP BY firm, part, price) a
  JOIN (SELECT firm
             , SUM(price) TotPri
          FROM ithelp160202a
         GROUP BY firm
       ) b
 USING (firm)
 ORDER BY firm, part; 

FIRM PART      PRICE     TOTPRI
---- ---- ---------- ----------
A    123         100        300
A    456         200 {NULL}
B    789         300        300