T-SQL - 连接多个表会导致重复的行

Question

我很想从下面的示例小提琴中得到以下结果.

结果:

来源表:

小提琴

我们的想法是RecordID通过查找预算和预测ID 的最大数量来创建单个行,以创建其他列(如果不存在该预算或预测ID的值,则将列单元格保留为空).

我尝试了PIVOT功能,但无法得到一个不错的结果.

更新:请参阅下图,我试图解释预期的输出:

用语言:对于属于RecordID的每个 BudgetID,为BDate,Result(Percentage*BAmount of Records表)和Status创建单独的列.

在我的示例中,RecordID 55在Budget表中有两个条目 - 因此需要2x3列来显示此RecordID 的单行中每个日期,结果和状态.

由于RecordID 77在Budget表中具有最多(三个)条目,因此它用于在所有行上创建3x3列.

预测也是如此.

我希望你能帮助我.

谢谢.

Answer 1

美好的一天,

注意!我的目标是帮助读者学习而不是提供最终查询作为他的家庭作业的解决方案.因此,我将分两步介绍解决方案,并在动态解决方案中添加几个"PRINT"命令,以便读者可以选择检查工作中的中间步骤.

OP提供的DDL + DML:

DROP TABLE IF EXISTS Budget;
CREATE TABLE Budget
    (BudgetID int, RecordID int, BDate date,Percentage int, [Status] varchar(50));
INSERT INTO Budget
    (BudgetID, RecordID, BDate,Percentage,Status)
VALUES
    (1, 55, '2017-01-01', 60, 'ordered'),
    (2, 55, '2017-03-24', 40, 'ordered'),
    (3, 66, '2018-08-15', 100, 'invoiced'),
    (4, 77, '2018-12-02', 25, 'paid'),
    (5, 77, '2018-09-10', 35, 'ordered'),
    (6, 77, '2019-07-13', 40, 'ordered')
GO

DROP TABLE IF EXISTS Forecast;
CREATE TABLE Forecast
    (ForecastID int, RecordID int, FDate date, Percentage int);
INSERT INTO Forecast
    (ForecastID, RecordID, FDate,Percentage)
VALUES
    (1, 55, '2020-12-01', 100),
    (2, 77, '2023-05-17', 25),
    (3, 77, '2024-11-28', 75)
GO

DROP TABLE IF EXISTS Records;
CREATE TABLE Records
    (RecordID int, BAmount int, FAmount int, Name varchar(40), Description varchar(40) )
;
INSERT INTO Records
   (RecordID, BAmount,FAmount,Name, Description)
VALUES
    (55, 15000, 33000, 'Prod1', 'Desc1' ),
     (66, 22000, 17500, 'Prod2', 'Desc2' ),
    (77, 40000, 44000, 'Prod3', 'Desc3' )
GO

select * from Budget
select * from Forecast
select * from Records

让我们首先展示一个简单的静态解决方案

这基于我们知道,对于Budget表中的每个RecordID,我们最多有三行,而对于Forecast表中的每个RecordID,最多有两行.这有助于理解我接下来要展示的动态解决方案

;With CteBudget as (
    select 
        b.BDate, b.BudgetID, b.Percentage, b.RecordID, b.Status
        ,RN = ROW_NUMBER() OVER (partition by b.RecordID order by b.BudgetID)
    from Budget b
),
CteForecast as (
    select 
        f.FDate, f.ForecastID, f.Percentage, f.RecordID
        ,RN = ROW_NUMBER() OVER (partition by f.RecordID order by f.ForecastID)
    from Forecast f
)
select 
    r.RecordID, r.Name, r.Description, 

    b1.BDate BDate1, (b1.Percentage * r.BAmount)/100 BResult1, b1.Status BStatus1, 
    b2.BDate BDate2, (b2.Percentage * r.BAmount)/100 BResult2, b2.Status BStatus2,
    b3.BDate BDate3, (b3.Percentage * r.BAmount)/100 BResult3, b3.Status BStatus3, 

    f1.FDate FDate1, (f1.Percentage * r.BAmount)/100 FResult1,
    f2.FDate FDate2, (f2.Percentage * r.BAmount)/100 FResult2

from Records r
left join CteBudget b1 on r.RecordID = b1.RecordID and b1.RN = 1
left join CteBudget b2 on r.RecordID = b2.RecordID and b2.RN = 2
left join CteBudget b3 on r.RecordID = b3.RecordID and b3.RN = 3
left join CteForecast f1 on r.RecordID = f1.RecordID and f1.RN = 1
left join CteForecast f2 on r.RecordID = f2.RecordID and f2.RN = 2
--where r.RecordID = 77
GO

注意!对于静态解决方案而没有索引(我将在最后添加),上述解决方案在性能方面非常糟糕,但是一旦我们添加正确的索引并作为动态解决方案的基础,此选项应该很合适.

现在我们可以呈现动态解决方案.

-- Get number of columns
Declare @NumBudget tinyint
Declare @NumForecast tinyint
SELECT @NumBudget = MAX(C) FROM (
    select COUNT(RecordID) C
    from Budget
    GROUP BY RecordID
) t
SELECT @NumForecast = MAX(C) FROM (
    select COUNT(RecordID) C
    from Forecast
    GROUP BY RecordID
) t
---------------------------------------------
DECLARE @SQLString1 nvarchar(MAX) = '';
DECLARE @SQLString2 nvarchar(MAX) = '';
DECLARE @loop int = 1;
WHILE @loop <= @NumBudget BEGIN 
    SET @SQLString1 = @SQLString1 + N'
    b' + CONVERT(VARCHAR(2),@loop) + '.BDate BDate' + CONVERT(VARCHAR(2),@loop) + ', (b' + CONVERT(VARCHAR(2),@loop) + '.Percentage * r.BAmount)/100 BResult' + CONVERT(VARCHAR(2),@loop) + ', b' + CONVERT(VARCHAR(2),@loop) + '.Status BStatus' + CONVERT(VARCHAR(2),@loop) + ', '

    SET @SQLString2 = @SQLString2 + N'
    left join CteBudget b' + CONVERT(VARCHAR(2),@loop) + ' on r.RecordID = b' + CONVERT(VARCHAR(2),@loop) + '.RecordID and b' + CONVERT(VARCHAR(2),@loop) + '.RN = 1'

    SET @loop = @loop + 1
END
SET @loop = 1

WHILE @loop <= @NumForecast BEGIN  
    SET @SQLString1 = @SQLString1 + N'
    f' + CONVERT(VARCHAR(2),@loop) + '.FDate FDate' + CONVERT(VARCHAR(2),@loop) + ', (f' + CONVERT(VARCHAR(2),@loop) + '.Percentage * r.BAmount)/100 FResult' + CONVERT(VARCHAR(2),@loop) + ','

    SET @SQLString2 = @SQLString2 + N'
    left join CteForecast f' + CONVERT(VARCHAR(2),@loop) + ' on r.RecordID = f' + CONVERT(VARCHAR(2),@loop) + '.RecordID and f' + CONVERT(VARCHAR(2),@loop) + '.RN = 1'

    SET @loop = @loop + 1
END
SET @SQLString1 = STUFF (@SQLString1, LEN(@SQLString1) , 1 , '')  
PRINT '/************************************************/'
PRINT @SQLString1
PRINT @SQLString2
PRINT '/************************************************/'

DECLARE @SQLString nvarchar(MAX);
SET @SQLString = N'
;With CteBudget as (
    select 
        b.BDate, b.BudgetID, b.Percentage, b.RecordID, b.Status
        ,RN = ROW_NUMBER() OVER (partition by b.RecordID order by b.BudgetID)
    from Budget b
),
CteForecast as (
    select 
        f.FDate, f.ForecastID, f.Percentage, f.RecordID
        ,RN = ROW_NUMBER() OVER (partition by f.RecordID order by f.ForecastID)
    from Forecast f
)
select 
    r.RecordID, r.Name, r.Description, 
'
+ @SQLString1
+ N'
from Records r'
+ @SQLString2

print @SQLString

EXECUTE sp_executesql @SQLString
GO

重要!此解决方案不一定是提供最佳性能的解决方案,而是可能最容易遵循和理解的解决方案.在生产一旦我们将拥有真正的DDL + DML并且服务器将具有统计数据,那么我们将能够改进性能并为我们的特定情况选择最佳解决方案.

索引

注意!上面的解决方案可能导致大量的数据排序,并且拥有正确的索引在这里非常重要!测试几种不同的选项并选择最佳选项非常重要.

为了论坛(或者你称之为stackoverflow,我认为不是讨论论坛界面而是问答界面),我添加查询来创建CLUSTERED INDEX,我假设你在制作中有一个,以及一个可选的NONCLUSTERED INDEX你应该测试(我没有测试其他选项,这意味着第一个出现在我脑海中,所以建议用真正的DDL + DML检查正确的索引).

-- CLUSTERED INDEX
CREATE CLUSTERED INDEX IX_Budget_BudgetID
    ON dbo.Budget (BudgetID);   
GO 
CREATE CLUSTERED INDEX IX_Forecast_ForecastID
    ON dbo.Forecast (ForecastID);   
GO 
CREATE CLUSTERED INDEX IX_Records_RecordID  
    ON dbo.Records (RecordID);   
GO 

-- NONCLUSTERED INDEX
CREATE NONCLUSTERED INDEX NX_Budget_RecordID_BudgetID
    ON dbo.Budget (RecordID,BudgetID);   
GO 
CREATE NONCLUSTERED INDEX NX_Forecast_RecordID_ForecastID
    ON dbo.Forecast (RecordID,ForecastID);   
GO 
CREATE NONCLUSTERED INDEX NX_Records_RecordID_RecordID  
    ON dbo.Records (RecordID);   
GO