如何從MySQL的同一張表中減去兩個計算字段？

Question

SELECT   *, 
         SUM(price+shipping+paypalfee+storefee) AS totalcost, 
         customerpaid                           AS totalrevenue, 
         (totalcost - totalrevenue)             AS profit 
FROM     tblsales 
GROUP BY orderno 
HAVING   " . $having . " 
ORDER BY $sort $order 
LIMIT    $offset,$rows

如果我忽略(totalcost - totalrevenue) as profit則查詢工作正常。 如何使用totalcost和totalrevenue在同一查詢中計算利潤？

Answer 1

您問題的答案是必須重復以下表達式：

select *, sum(price+shipping+paypalfee+storefee) as totalcost
       customerpaid as totalrevenue,
       (sum(price+shipping+paypalfee+storefee) - customerpaid) as profit
from tblsales
group by orderno
having " . $having . "
order by $sort $order
limit $offset, $rows;

不允許在定義別名的同一select中使用列別名。

而且，您的查詢看起來很奇怪。 任何具有select *和group by查詢都是可疑的。 您有許多列（大概），其值將來自每個組的不確定行。 通常，您應該顯式列出各列，但對於group by則應特別列出。

Answer 2

您可以這樣執行：SELECT *，（總成本-總收入）AS利潤，FROM（SELECT *，SUM（價格+運費+ Paypalfee +商店費用）AS總成本，客戶支付的AS總收入，

從tblsales GROUP BY orderno擁有“。$ having。” ORDER BY $ sort $ order）LIMIT $ offset，$ rows