mysql - 替换子查询

Question

我试图根据画家的身份证号码，在扣除画廊佣金后显示该画家的总收入。这是我目前所拥有的:

SELECT painter.ptr_num, painter.ptr_firstname, (SUM() - 
(gallery.gal_rate*painting.ptng_price)) AS Earnings
FROM painting,painter,gallery
GROUP BY painter.ptr_num

您可能已经注意到，总和为空，这是因为我能想到的实现上述目标的唯一方法是使用子查询。

这里是求和必须包含的Painting表:

绘画

Ptng_Price     Ptr_Num
       24                  100
       85                  101
       34                  102
       17                  103

任何额外信息将应要求提供。在此先感谢您的帮助!

ERD...

Answer 1

假设绘画表中的所有记录都是“已售出”绘画，因此应该汇总(求和)到收入中。

这是基于每幅画计算收入，然后按数字和名字分组汇总

SELECT P.ptr_num, 
       P.ptr_firstname, 
       sum(obj.ptng_price - (G.gal_rate*obj.ptng_price)) AS Earnings
FROM painting obj
INNER JOIN painter P
 on obj.Ptr_num = P.Ptr_num
INNER JOIN gallery G
 on obj.Gal_num = G.Gal_Num
GROUP BY P.ptr_num, 
       P.ptr_firstname,