SQL 加入总和

Question

先生，我有 3 SQL tables 即库存、采购和销售。在库存 table 中，我有 SKU、数量、MRP 等字段在购买 table 中，我有 SKU、purch_qty、purch_date 等字段。在已售出的 table 中，我有 SKU、sold_qty、sold_date 等字段

我的查询是当我想创建一个视图时，我可以在其中查看所有初始数量为 sold_qty、puch_qty、availabe_Qty 的 SKU，例如（SKU，initial_qty, purchased_qty, sold_qty, stock_availabe)

我尝试在 SKU 上加入这些 table，但结果是数量的两倍。

你能帮我解决这个问题吗？

我的sql查询码是

    SELECT        stk.id, stk.sku, SUM(stk.qty) AS Initial_Qty, SUM(pur.qty) AS Purch_Qty, SUM(sld.qty) AS Sold_Qty
FROM            dbo.stock AS stk LEFT OUTER JOIN
                         dbo.sold AS sld ON stk.sku = sld.sku LEFT OUTER JOIN
                         dbo.purchase AS pur ON stk.sku = pur.sku
GROUP BY stk.id, stk.sku

Answer 1

基本上，您需要在加入之前在子查询中进行聚合。您想要的逻辑应该如下所示：

select st.sku, st.qty stock_qty, pu.purch_qty, so.sold_qty
from stock st
left join (select sku, sum(purch_qty) purch_qty from purchase group by sku) pu 
    on pu.sku = st.sku
left join (select sku, sum(sold_qty) sold_qty from sold group by sku) so
    on so.sku = st.sku

SQL 加入总和

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