加入一个 table 与标签的重复条目但不是 ID 列

Question

我有以下 table Fact_Sales :

ProductSK DateSK SalesAmount SalesNumber 
1         2019   300         150 
2         2019   500         190 
.....

和以下 table DimProduct：

ProductSK CategoryLabel 
1         ABC 
2         ABC 
....

我想按类别标签计算销售额，但是当像下面这样加入时，查询结果生成笛卡尔积：

SELECT CategoryLabel, SUM(SalesAmount)
FROM    Fact_Sales,     DimProduct

Answer 1

您可以 LEFT 连接到产品的不同值 table :

SELECT DP.CategoryLabel, SUM(FS.SalesAmount)
FROM Fact_Sales AS FS
LEFT JOIN (
SELECT DISTINCT ProductSK,CategoryLabel FROM DimProduct
) AS DP
ON DP.ProductSK=FS.ProductSK
GROUP BY DP.CategoryLabel

Answer 2

您应该使用 INNER JOIN ON：

SELECT CategoryLabel, SUM(F.SalesAmount)
FROM Fact_Sales AS F INNER JOIN DimProduct AS D ON F.ProductSK = D.ProductSK
GROUP BY D.CategoryLabel

加入一个 table 与标签的重复条目但不是 ID 列

Join a table with duplicate entries for a label but not for the ID column

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