MS Access SQL 中的两个聚合函数？

Question

SELECT c.Category, SUM(c.[Market Value]), SUM([p.Market Value])
FROM Dec AS c, [NOV] as p
GROUP BY c.Category
;

告诉我类别不是聚合函数的一部分。 我只想查看两个表的每个类别的总和。 我不希望只出现某些值，所以我应该使用 Join 吗？

编辑：

SELECT c.[Category],  SUM(c.[Market Value]), SUM(p.[Market Value])
FROM Dec AS c
INNER JOIN Nov AS p ON c.ID = p.ID
GROUP BY c.category, p.Category
;

这是我使用 JOIN 编写的内容，它只是不间断地运行查询。 我就等着吗？ 80000行数据，做一个按类别分组的SUM只做了一个月，瞬间就回本了，为什么做两张表这么难？

Answer 1

您需要联合所有数据：

SELECT Category, [market Value]
FROM DEC
UNION ALL 
SELECT Category, [market Value]
FROM NOV

运行此查询时，您将获得两个月的合并数据。 如果您想获得组合数据的总和，只需使用查询：

SELECT Category, SUM([market Value]) as sum_value
FROM (
SELECT Category, [market Value]
FROM DEC
UNION ALL 
SELECT Category, [market Value]
FROM NOV
) as A
GROUP BY Category

现在，这不是你想要的。 您需要两列：一列用于 11 月，一列用于 12 月。为此，您需要稍微修改 UNION ALL 查询：

SELECT Category, [market Value], 'Dec' as type
FROM DEC
UNION ALL 
SELECT Category, [market Value], 'Nov' as type
FROM NOV

最后的查询将是：

SELECT Category, 
SUM(iif(type='Dec', [Market Value], 0)) as Dec_Value, 
SUM(iif(type='Nov', [Market Value], 0)) as Nov_Value
FROM (
SELECT Category, [market Value], 'Dec' as type
FROM DEC
UNION ALL 
SELECT Category, [market Value], 'Nov' as type
FROM NOV
) as A
GROUP BY Category