我对SQL还不陌生，因此我试图在特定日期获取产品交易的价格，即在价格目录中查找交易之前该产品的最新价格。
具体来说，我有以下两个表：
Transactions Catalog
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ProductID | Design | Transaction_DT ProductID | Price | Effective_DT
1 | Plaid | 5/14/2016 1 | 20 | 4/22/2016
2 | Solid | 3/26/2016 1 | 10 | 5/2/2016
3 | PolkaDot | 4/12/2016 1 | 5 | 5/15/2016
4 | Solid | 4/24/2016 2 | 50 | 3/22/2016
5 | PolkaDot | 2/24/2016 2 | 25 | 4/1/2016
6 | PinStripe | 3/29/2016 2 | 10 | 4/2/2016
3 | 30 | 4/5/2016
3 | 25 | 4/9/2016
3 | 22 | 4/12/2016
4 | 12 | 3/15/2016
4 | 8 | 3/27/2016
4 | 6 | 4/25/2016
5 | 15 | 2/23/2016
5 | 11 | 2/25/2016
5 | 6 | 2/28/2016
6 | 26 | 2/2/2016
6 | 17 | 3/19/2016
6 | 13 | 5/16/2016
我输入了以下代码：
SELECT Transactions.ProductID,
Catalog.Price,
Transactions.Transaction_DT,
Transactions.Design
FROM Transactions
LEFT JOIN
Catalog ON Transactions.ProductID = Catalog.ProductID AND
Catalog.Effective_DT = (
SELECT MAX(Effective_DT)
FROM Catalog
WHERE Effective_DT <= Transactions.Transactions DT
)
并获得以下输出：
ProductID | Price | Transaction_DT | Design
1 | Null | 5/14/2016 | Plaid
2 | 50 | 3/26/2016 | Solid
3 | 22 | 4/12/2016 | PolkaDot
4 | Null | 4/24/2016 | Solid
5 | 15 | 2/24/2016 | PolkaDot
6 | Null | 3/29/2016 | PinStripe
我想将产品1、4和6的价格分别返回10、8和17（除了正确输出的正确价格），而不是我得到的Null值。关于如何获得适当结果的任何想法？
最佳答案
您忘记了按productID过滤相关查询。您没有得到正确的产品最新日期。您需要使用以下查询：
SELECT Transactions.ProductID,
Catalog.Price,
Transactions.Transaction_DT,
Transactions.Design
FROM Transactions
LEFT JOIN
Catalog ON Transactions.ProductID = Catalog.ProductID AND
Catalog.Effective_DT = (
SELECT MAX(Effective_DT)
FROM Catalog
WHERE Effective_DT <= Transactions.Transactions_DT
and ProductID = Transactions.ProductID
)
关于sql - SQLiteStudio:从价格目录中获取最新价格，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/38085053/