獲取T-SQL中所有最新價格的價格變化

Question

我的任務是編寫一個允許用戶搜索價格表的應用程序，其中價格在3個不同的鍵上唯一，例如狀態，出版商，和型（可能有任何數量的與任何3個字段的相同的密鑰值的行，但僅存在一個行與狀態 =「俄亥俄」，出版商 =」 Bob'，並且類型 ='硅'）。當用戶選擇狀態和出版商，他們提出的所有類型與狀態和出版商的列表。我運行一個存儲過程來提取這些項目，並且我拉取最近的價格，但是我也需要拉第二個最近的價格，並進行數學計算，以便將價格變化顯示給用戶。目前，我創建了以下函數，但是它會使我的存儲過程減慢1到40秒，具體取決於服務器在執行時的心情。

BEGIN 
    -- Declare the return variable here 
    DECLARE @priceChange float 
    DECLARE @currentPriceDate date 
    DECLARE @currentPrice float 
    DECLARE @previousPrice float 

    -- Add the T-SQL statements to compute the return value here 
    SELECT TOP 1 @currentPriceDate=PriceDate ,@CurrentPrice=MarketPrice 
     FROM MarketPrice_Table 
      LEFT JOIN PriceEffectiveDate_Table ON MarketPrice_Table.PriceDate = PriceEffectiveDate_Table.EffectiveDate 
       AND MarketPrice_Table.PublisherID = PriceEffectiveDate_Table.PublisherID 
     WHERE TypeID = @TypeID 
     AND MarketPrice_Table.PublisherID = @PublisherID 
     AND MarketPrice_Table.StateID = @StateID 
     ORDER BY PriceDate DESC; 

    SET @previousPrice = (SELECT TOP 1 MarketPrice 
     FROM MarketPrice_Table 
      LEFT JOIN PriceEffectiveDate_Table ON MarketPrice_Table.PriceDate = PriceEffectiveDate_Table.EffectiveDate 
       AND MarketPrice_Table.PublisherID = PriceEffectiveDate_Table.PublisherID 
     WHERE TypeID = @TypeID 
     AND MarketPrice_Table.PublisherID = @PublisherID 
     AND MarketPrice_Table.StateID = @StateID 
     AND MarketPrice_Table.PriceDate <> @currentPriceDate 
     ORDER BY PriceDate DESC); 

    SET @priceChange = @currentPrice - @previousPrice; 

    -- Return the result of the function 
    RETURN @priceChange 

END 

是否有更有效的方法來做到這一點，所以我不在存儲過程中每行兩個查詢？

非常感謝您的幫助，如果我能進一步澄清，請告訴我！

Answer 1

嘗試使用LEAD分析功能和使用它在一個表中返回的數據。我很抱歉，如果這不是確切的，但有一些修改，我相信它會給你你想要的。

嘗試：

DECLARE @priceChange float 
DECLARE @currentPriceDate date 
DECLARE @currentPrice float 
DECLARE @previousPrice FLOAT 

SELECT 
    * 
FROM 
    ( 
     SELECT 
      ROW_NUMBER() OVER (PARTITION BY MarketPrice_Table.StateID, MarketPrice_Table.PublisherID, TypeID ORDER BY PriceDate DESC) AS RowNum, 
      MarketPrice_Table.StateID, 
      MarketPrice_Table.PublisherID, 
      TypeID, 
      PriceDate, 
      MarketPrice AS CurrentPrice, 
      LEAD(MarketPrice) OVER (PARTITION BY MarketPrice_Table.StateID, MarketPrice_Table.PublisherID, TypeID ORDER BY PriceDate DESC) AS PreviousPrice, 
      MarketPrice - ISNULL(LEAD(MarketPrice) OVER (PARTITION BY MarketPrice_Table.StateID, MarketPrice_Table.PublisherID, TypeID ORDER BY PriceDate DESC), 0) AS PriceChange 
     FROM 
      MarketPrice_Table 
      LEFT JOIN PriceEffectiveDate_Table 
       ON MarketPrice_Table.PriceDate = PriceEffectiveDate_Table.EffectiveDate 
       AND MarketPrice_Table.PublisherID = PriceEffectiveDate_Table.PublisherID 
     WHERE 
      TypeID = @TypeID AND 
      MarketPrice_Table.PublisherID = @PublisherID AND 
      MarketPrice_Table.StateID = @StateID 
    ) r 
WHERE 
    r.RowNum = 1 

Answer 2

試試這個請：

BEGIN 
-- Declare the return variable here 
DECLARE @priceChange float 
DECLARE @currentPriceDate varchar(8) 
DECLARE @currentPrice float 
DECLARE @previousPrice float 

-- Add the T-SQL statements to compute the return value here 
SELECT TOP 1 @currentPriceDate=Convert(varchar,PriceDate,112) ,@CurrentPrice=MarketPrice 
    FROM MarketPrice_Table 
     LEFT JOIN PriceEffectiveDate_Table ON Convert(varchar,MarketPrice_Table.PriceDate,112) = Convert(varchar,PriceEffectiveDate_Table.EffectiveDate,112) 
      AND MarketPrice_Table.PublisherID = PriceEffectiveDate_Table.PublisherID 
    WHERE TypeID = @TypeID 
    AND MarketPrice_Table.PublisherID = @PublisherID 
    AND MarketPrice_Table.StateID = @StateID 
    ORDER BY PriceDate DESC; 

SET @previousPrice = (SELECT TOP 1 MarketPrice 
    FROM MarketPrice_Table 
     LEFT JOIN PriceEffectiveDate_Table ON Convert(varchar,MarketPrice_Table.PriceDate,112) = Convert(varchar,PriceEffectiveDate_Table.EffectiveDate) 
      AND MarketPrice_Table.PublisherID = PriceEffectiveDate_Table.PublisherID 
    WHERE TypeID = @TypeID 
    AND MarketPrice_Table.PublisherID = @PublisherID 
    AND MarketPrice_Table.StateID = @StateID 
    AND Convert(varchar,MarketPrice_Table.PriceDate,112) <> @currentPriceDate 
    ORDER BY PriceDate DESC); 

SET @priceChange = @currentPrice - @previousPrice; 

-- Return the result of the function 
RETURN @priceChange 

END