使用计算字段连接两个子查询

Question

我有两个表格，其中包含有关两个小部件的生产信息。 Table1 看起来像这样：

表 2 如下所示：

我想计算每个小部件的平均产量并按国家代码 (ADM0_A3) 显示，以便结果看起来像这样（在此阶段不必担心丢失数据，例如。 BWA 没有生产 widget1)

ADM0_A3   w1avg   w2avg
DZA      50000  3450000
AGO      86000    40000
BWA      blank        0
CMR       3500    blank

我正在使用的 MS ACCESS SQL 查询在这里：

SELECT Z.ccode, Z.ave_w1, A.ave_w2 
FROM 
(
    SELECT X.ADM0_A3 as ccode, 0.02 * X.sum_w1 / X.n_w1 AS ave_w1 
    FROM 
    (
        SELECT t1.ADM0_A3, SUM(t1.production) AS sum_w1, COUNT(t1.production) as n_w1 
        FROM Table1 t1
        GROUP BY t1.ADM0_A3
    ) X
) Z
JOIN
( 
    SELECT Y.ADM0_A3, 0.025 * Y.sum_w2 / Y.n_w2 AS ave_w2
    FROM 
    (
        SELECT t2.ADM0_A3, SUM(t2.production) AS sum_w2, COUNT(t2.production) as n_w2 
        FROM Table2 t2
        GROUP BY t2.ADM0_A3
    ) Y
) A
ON A.ADM0_A3 = Z.ccode

我检查了子查询，它们工作正常。但是，当我尝试加入查询时，我收到此错误消息 "Syntax error in FROM clause"。我认为解决方案相当简单，但我看不到它，所以不胜感激任何建议。提前致谢！

Answer 1

您可以尝试这样做：

SELECT adm0_a3, MAX(w1avg) as w1avg, MAX(w2avg) as w2avg
FROM (SELECT t1.ADM0_A3, AVG(t1.production) * 0.02 as w1avg, NULL as w2avg
      FROM Table1 as t1
      GROUP BY t1.ADM0_A3
      UNION ALL
      SELECT t2.ADM0_A3, NULL, AVG(t2.production) * 0.02 as w1avg
      FROM Table1 as t2
      GROUP BY t2.ADM0_A3
     ) as t
GROUP BY adm0_a3;

我不确定是否所有版本的 MS Access 都支持 FROM 子句中的 UNION ALL。如果没有，您可以使用视图来解决这个问题。

使用计算字段连接两个子查询

JOINing two sub-queries with calculated fields

sql

ms-access-2016