Question

由于某些未知原因，查询将两个SUM字段相互相乘：

表格

products table
+----+--------+
| id | p_name |
+----+--------+
|  1 | name1  |
|  2 | name2  |
+----+--------+

warehouses table:
+----+------------+
| id |   w_name   |
+----+------------+
|  1 | warehouse1 |
|  2 | warehouse2 |
+----+------------+

intake table:
+--------------+------------+--------+
| warehouse_id | product_id | amount |
+--------------+------------+--------+
|            1 |          1 |     10 |
|            1 |          1 |     10 |
+--------------+------------+--------+

outtake table
+--------------+------------+--------+
| warehouse_id | product_id | amount |
+--------------+------------+--------+
|            1 |          1 |      5 |
|            1 |          1 |      5 |
+--------------+------------+--------+

查询

SELECT warehouses.w_name,
       products.p_name,
       Sum(intake.units_amout) AS intakeSum,
       Sum(outtake.amount) AS outtakeSum
FROM (warehouses
      INNER JOIN (products
                  INNER JOIN intake ON products.id = intake.product_id) ON warehouses.id = intake.warehouse_id)
INNER JOIN outtake ON (warehouses.id = outtake.warehouse_id)
AND (products.id = outtake.product_id)
GROUP BY warehouses.w_name,
         products.p_name;

结果

+--------------+------------+-----------+------------+
| warehouse_id | product_id | intakeSum | outtakeSum |
+--------------+------------+-----------+------------+
|            1 |          1 |        40 |         20 |
+--------------+------------+-----------+------------+

预期结果

+--------------+------------+-----------+------------+
| warehouse_id | product_id | intakeSum | outtakeSum |
+--------------+------------+-----------+------------+
|            1 |          1 |        20 |         10 |
+--------------+------------+-----------+------------+

如果我添加第三个入口（使用相同的产品和仓库ID），“outtakeSum”将乘以3！等等..

Answer 1

这是因为如果使用输出表进入连接将导致总共四行导致总和为4 * 10 = 40和4 * 5 = 20。

为了解决这个问题，你可以做两个子查询，一个用于入口和出口表，每个子表将为每个warehouse_id / product_id对汇总这些表。

即：

SELECT warehouse_id, product_id, SUM(amount)
FROM intake
GROUP BY warehouse_id, product_id;

（和出口表的类似查询）

如果您使用这些查询而不是摄入量和加入时，它将按预期工作。

为什么Access会相互乘以两个SUM？

1 个答案: