Sql server 为什么在SQL Server 2012中连接两个表变量会显著增加执行时间

我正在将数据提取到两个表变量

@PremiumData

和

@LossData

。连接列为

ControlNo

如果单独运行它们，则填充

@PremiumData

的执行时间为3秒，填充

@LossData

的执行时间为0秒

但是，当我通过

左连接将它们连接在一起时，执行时间将增加到01:07！分钟

查询计划可在此处找到：

这也是执行计划中与我有关的部分：

查看链接的执行计划中表变量的估计行数。估计值是1行，但实际行要高得多

问题是基数估计值太离谱了。我猜想这个查询会导致临时数据库溢出，因为初始内存授予太低了。有一些

尝试使用临时表而不是表变量

您还可以尝试在
insert
语句（表变量或临时表）的末尾添加
选项（重新编译）
，这将改进基数估计

基于您的编辑进行编辑：该排序也受到基数估计错误的影响。排序之所以存在，是因为您正在对连接两个表变量的查询进行分组。
尝试使用temp#table而不是table变量，因为表变量对于大量行，尤其是基数估计有性能问题。通过使用#TELLATES，现在的执行时间是3秒。令人惊叹的。非常感谢。
DECLARE
    @EffectiveDateFrom DATETIME = '2012-04-01',
    @EffectiveDateTo DATETIME = '2018-04-30'

DECLARE @PremiumData TABLE (
                            ControlNo int,
                            PolicyNumber varchar(50),
                            EffectiveDate datetime,
                            ExpirationDate datetime,
                            ProducerName varchar(300), 
                            Premium money
                           )
DECLARE @LossData TABLE (
                        ControlNo int,
                        Losses money
                        )

INSERT INTO @PremiumData
    SELECT 
        INV.QuoteControlNum,  
        tblQuotes.PolicyNumber,
        tblQuotes.EffectiveDate,
        (SELECT TOP 1 Q.ExpirationDate
         FROM tblQuotes Q
         WHERE Q.ControlNo = tblQuotes.ControlNo
         ORDER BY Q.QuoteID DESC) as ExpirationDate,
        tblProducers.ProducerName,
        (SELECT ISNULL(SUM(tblFin_InvoiceDetails.AmtBilled), 0)
         FROM tblFin_InvoiceDetails
         WHERE (tblFin_InvoiceDetails.ChargeType = 'P')
           AND (tblFin_InvoiceDetails.InvoiceNum = INV.InvoiceNum)) AS Premium
    FROM            
        tblFin_Invoices INV
    INNER JOIN      
        tblQuotes ON INV.QuoteID = tblQuotes.QuoteID
    INNER JOIN      
        tblProducerLocations ON INV.ProducerLocationGUID = tblProducerLocations.ProducerLocationGUID
    LEFT OUTER JOIN 
        tblProducers WITH (NOLOCK) ON tblProducerLocations.ProducerGUID = dbo.tblProducers.ProducerGUID 
    WHERE 
        (INV.Failed = 0)  
        AND (DATEDIFF(dd, tblQuotes.EffectiveDate, ISNULL(@EffectiveDateTo, tblQuotes.EffectiveDate)) >= 0)
        AND (DATEDIFF(dd, ISNULL(@EffectiveDateFrom, tblQuotes.EffectiveDate), tblQuotes.EffectiveDate) >= 0)
        AND dbo.tblQuotes.CompanyLocationGUID IN ('32828BB4-E1FA-489F-9764-75D8AF7A78F1',--"Plaza Insurance Company"    
                                                  '54A8FCCD-C7FE-4642-9C22-3A25207CDAEE' -- Watford         
                                                 )   

INSERT INTO @LossData
    SELECT 
        CPI.ControlNumber,
        SUM(CRP.ResPayAmount) as [Losses]
    FROM
        tblClaims_Claim C
    INNER JOIN 
        tblClaims_PolicyInformation CPI ON CPI.ClaimId = C.ClaimId
    INNER JOIN 
        tblClaims_ReservePayments CRP ON CRP.ClaimId = C.ClaimId
    GROUP BY
        CPI.ControlNumber--,

/* Joining @PremiumData and @LossData*/
SELECT  
    p.PolicyNumber,
    CONVERT(VARCHAR(11),p.EffectiveDate,101) as EffectiveDate,
    YEAR(EffectiveDate) as EffectiveYear,
    MONTH(EffectiveDate) as EffectiveMonth,
    SUBSTRING('JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ', (MONTH(EffectiveDate) * 4) - 3, 3) as MonthShort,
    'Q' + CONVERT(CHAR(1),DATEPART(QUARTER, p.EffectiveDate)) as Quarter,
    p.ProducerName,
    SUM(p.Premium) as Premium,
    ISNULL(ROUND(dbo.fn_EarnedPremiumCalcExtendedPolicies(SUM(Premium), EffectiveDate, ExpirationDate, 0, GETDATE()), 2), SUM(Premium)) AS EarnedPremium,   
    ISNULL(l.Losses,0) as Losses,
    ISNULL(SUM(l.Losses), 0) / NULLIF(ISNULL(ROUND(dbo.fn_EarnedPremiumCalcExtendedPolicies(SUM(Premium), EffectiveDate, ExpirationDate, 0, GETDATE()), 2), SUM(Premium)),0) as LossRatio
FROM 
    @PremiumData p
LEFT JOIN 
    @LossData l ON p.ControlNo = l.ControlNo 
GROUP BY  --p.ControlNo
    p.PolicyNumber,
    p.EffectiveDate,
    p.ExpirationDate,
    p.ProducerName,
    l.Losses