SQL查询连接4个表并从2个不同的表中获取2列的总和

Question

表1：购买报告

|id| VoucherNO| VoucherDate|
+--+----------+------------+
|1 |  0001    |  28/9/2017 |
|2 |  0010    |  27/9/2017 |

表2：明细购买报告

|id | ITEMID | QTYpurchased | voucher
+---+--------+--------------+--------
|1  |   101  | 12           |   0001
|2  |   120  | 25           |   0001
|3  |   121  | 21           |   0014

表3：销售报告

|id| VoucherNO| VoucherDate|
+--+----------+------------+
|1 |  0025    |  25/9/2017 |
|2 |  0058    |  23/9/2017 |

表4：明细销售

|id | ITEMID | QTYpurchased | voucher
+---+--------+--------------+--------
|1  |  101   |  8           |   0025
|2  |  120   |  5           |   0025
|3  |  121   | 10           |   0058

查询的目的是连接所有4个表以返回2个列 即。，

• 第1栏：项目名称
• 2：差异已购买数量且已售出具有相同商品ID的数量 在给定日期之间给出该特定日期的项目数量。

我试过的查询如下

SELECT
  A.ITEMN, 
  A.ITEMNAME,
  SUM(CAST(C.QUANTITY AS numeric(18,2))) - SUM(CAST(A.QTY AS numeric(18,2))) as QTY 
FROM DETAILSALE A, SALESREPORT B, DETAILPURCHASES C, PURCHASEREPORT D 
WHERE A.BARCODE = B.VOUCHERNO 
  AND  C.BARCODE = D.VOUCHERNO 
  AND D.VOUCHERDATE=B.VOUCHERDATE
  AND D.VOUCHERDATE BETWEEN '" & DATE1.Text & "' AND '" & DATE2.Text & "'   
GROUP BY A.ITEMN,A.ITEMNAME 
ORDER BY A.ITEMN ASC

必需输出：

| ITEMID | QTY |
+--------+-----+
|  101   | 2   |
|  120   | 10  |
|  121   | 10  |

Answer 1

首先聚合，然后才加入。我错过了您的说明中的产品表格以及表格说明中的名称和查询不匹配，因此您可能需要在我的查询中调整名称：

select
  product.id,
  product.name,
  purchases.total,
  sales.total
from product
left join
(
  select itemid, sum(quantity) as total
  from detail_purchase
  where voucher in (select voucher from purchase where date between date '2017-09-01' 
                                                                and date '2017-09-05')
  group by itemid
) purchases on purchases.itemid = product.itemid
left join
(
  select itemid, sum(quantity) as total
  from detail_sale
  where voucher in (select voucher from sale where date between date '2017-09-01'
                                                            and date '2017-09-05')
  group by itemid
) sales on sales.itemid = product.itemid;

如果您只想要购买和/或销售的产品，请将外部连接更改为内部连接。