在 SQL Server 中使用 Sum Aggregate 函数进行内部联接
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Inner Join with Sum Aggregate function in SQL Server
提问by thevan
I have three tables StockSummary, Item, ItemSpecification. Here I want to join these three tables and to get Sum(StockSummary.Quantity). The main Columns are as follows:
我有三个表 StockSummary、Item、ItemSpecification。这里我想加入这三个表并得到 Sum(StockSummary.Quantity)。主要栏目如下：
TableA: StockSummary(ItemID, Quantity)
TableB: Item(ItemID, ItemName, SpecificationID)
TableC: ItemSpecification(SpecificationName, SpecificationID)
The desired result should give ItemName, SpecificationName and SUM(Quantity). How to use Aggregate function in Inner Joins?
所需的结果应提供 ItemName、SpecificationName 和 SUM(Quantity)。如何在内部联接中使用聚合函数？
回答by Alex K.
You aggregate the desired column & group by the remainder, the fact that the columns are from the result of a join is not relevant in your case;
您按余数聚合所需的列和组，列来自连接结果的事实与您的情况无关；
select
b.ItemName,
c.SpecificationName,
sum(a.Quantity)
from
tablea a
inner join tableb b on b.ItemID = a.ItemID
inner join tablec c on c.SpecificationID = b.SpecificationID
group by
b.ItemName,
c.SpecificationName
