Question

/*
Stored Procedure
April 30, 2021
Mohamad Chaker
*/

USE CIS111_BookStoreMC
GO
--drop the procedure
IF OBJECT_ID('spAssetInfo') IS NOT NULL
    DROP PROC spAssetInfo 
GO
--Create the stored procedure
CREATE PROC spAssetInfo

AS
--Create a temporary table to display the inventory
SELECT AssetID, Description, Cost, PurchaseDate 
INTO #temptable
FROM Assets

--Add a new column to the temporary table displaying the date an asset is completely depreciated
ALTER TABLE #temptable ADD CurrentValue MONEY

DECLARE @years INT;
DECLARE @currentYear INT;
SET @currentYear = YEAR(getdate());
DECLARE @cost MONEY;

--Add a new column to the temporary table to display the current value of the item in the current year
ALTER TABLE #temptable ADD CompleteDepreciationYear DATE

--@value holds the cost of an asset and is used to check when the value of an asset drops low
DECLARE @value MONEY;
SET @value = 0.00;
--@counter is an int that I used to iterate over the table rows
DECLARE @counter INT;
--@depreciationNum holds the amount of years until an item is completely depreciated to be later used in DATEADD() 
DECLARE @depreciationNum INT;
SET @counter = 1;

DECLARE @assetsTableSize INT;
SET @assetsTableSize = (SELECT COUNT(*) FROM Assets);

WHILE (@counter <= @assetsTableSize)
    BEGIN
        --Current Value
        SET @years = @currentYear - (select YEAR(PurchaseDate) From Assets Where AssetID = @counter);
        SET @cost = (select Cost From Assets Where AssetID = @counter);
        --calculate current value of each asset
        WHILE(@years>0)
            BEGIN
                SET @cost = @cost * 0.8;
                SET @years = @years - 1;
            END
        --add the current value of each asset to the temporary table
        UPDATE #temptable 
        SET CurrentValue = @cost
        WHERE AssetID = @counter;
        
        --Deprection Year
        SET @depreciationNum = 0;
        SET @value = (select Cost From Assets Where AssetID = @counter);
        WHILE(@value >0.1)
            BEGIN  
                SET @value = @value * 0.8;
                SET @depreciationNum = @depreciationNum + 1;
            END
        --add the date each asset is completely depreciated to the temporary table
        UPDATE #temptable 
        SET CompleteDepreciationYear = CAST(DATEADD(year, @depreciationNum, (select PurchaseDate From Assets Where AssetID = @counter)) AS DATE)
        WHERE AssetID = @counter;
        --increment the counter
        SET @counter = @counter + 1;
    END
--display the assets inventory
SELECT * FROM #temptable

提示：显示资产库存和当前价值（每年减去 20% 的折旧）。还显示每个项目的年份完全折旧。

基本上，我试图用 PurchaseDate 和项目完全折旧的日期来显示资产库存，资产每年折旧 20%。我尝试做一个临时表并将一些资产表列复制到其中，然后为资产完全折旧的日期添加一列。

我使用迭代解决方案实现了这一点，但有人建议我在 SO 上发帖，尝试使用基于集合的实现来执行此操作。我是 SQL 的新手，最近了解到它是一种基于集合的语言，并且不太适合迭代解决方案。

先谢谢你！

Answer 1

计算当前值的公式为：

CurrentValue = InitialValue * (1-0.2)^(Today - InitialDate)

要找到资产将达到 0.1 的 NumberOfYears：

0.1 = CurrentValue * (1-0.2)^NumberOfYears。从两边取日志：

Log(0.1) = Log(CurrentValue * Log(0.8^NumberOfYears)

Log(0.1) = Log(CurrentValue) + Log(0.8^NumberOfYears)

Log(0.1) = Log(CurrentValue) + NumberOfYears * Log(0.8)

[Log(0.1) - Log(CurrentValue)] / Log(0.8) = NumberOfYears

您可以创建一个使用此公式并返回 NumberOfYears 的函数：

CREATE  FUNCTION GetNumberOfYears(
    @InitialValue FLOAT
)
RETURNS FLOAT
AS
BEGIN
DECLARE @CurrentValue FLOAT,
        @InitialValue FLOAT,
        @YearsToZero FLOAT;

-- CurrentValue Formula
SET @CurrentValue = @InitialValue * POWER(CAST(0.8 AS FLOAT), YEAR(GETDATE() - YEAR(PurchaseDate));

-- NumberOfYears Formula
SELECT @YearsToZero = (LOG(0.1) - LOG(@CurrentValue)) / LOG(0.8);

RETURN @YearsToZero;
END

它会给你年数（例如 54.6724159 年）。

然后像 SELECT GetNumberOfYears(Cost) FROM Assets 一样使用它

或者，您可以直接从您的 SELECT 中使用：

SELECT
    Cost * POWER(CAST(0.85 AS FLOAT), YEAR(GETDATE()) - YEAR(PurchaseDate)) AS CurrentValue,
    (LOG(0.1) - LOG( [the above CurrentValue formula] )) / LOG(0.8) AS YearsToZero
 FROM Assets

如何将此迭代解决方案转换为基于集合的解决方案

1 个答案: