DB2中的GROUP BY AND RIGHT JOINS

Question

Select p.prodCode, 
     p.description, 
     p.unit, 
     SUM(sd.quantity) "Total quantity" 
FROM salesDetail sd 
RIGHT JOIN product p 
    ON p.prodCode = sd.prodCode 
GROUP BY p.prodCode 
ORDER BY 4 DESC 

Help！我的脚本没有运行。我需要得到每个产品的总数量，但是我的组没有工作。

Answer 1

计算在分开的子查询每个产品的数量的总和，然后加入此回原始product表：

SELECT t1.prodCode, 
     t1.description, 
     t1.unit, 
     t2.total_quantity 
FROM product t1 
INNER JOIN 
(
    SELECT p.prodCode, SUM(sd.quantity) total_quantity 
    FROM product p 
    LEFT JOIN salesDetail sd 
     ON p.prodCode = sd.prodCode 
    GROUP BY p.prodCode 
) t2 
    ON t1.prodCode = t2.prodCode 

注意，我通过切换连接的顺序替换RIGHT JOIN用LEFT JOIN子查询中的表。

更新：

如果你绝对需要使用RIGHT JOIN，则只需更换这个子查询：

SELECT p.prodCode, SUM(sd.quantity) total_quantity 
FROM salesDetail sd 
RIGHT JOIN product p 
    ON p.prodCode = sd.prodCode 
GROUP BY p.prodCode