Sql server 如何使用哈希匹配右外部联接提高SQL Server性能问题

我不熟悉性能问题。因此，我不确定我的方法应该是什么

这是一个运行时间超过7分钟的查询

INSERT INTO SubscriberToEncounterMapping(PatientEncounterID, InsuranceSubscriberID)
    SELECT 
        PV.PatientVisitId AS PatientEncounterID, 
        InsSub.InsuranceSubscriberID 
    FROM 
        DB1.dbo.PatientVisit PV 
    JOIN 
        DB1.dbo.PatientVisitInsurance PVI ON PV.PatientVisitId = PVI.PatientVisitId
    JOIN
        DB1.dbo.PatientInsurance PatIns on PatIns.PatientInsuranceId = PVI.PatientInsuranceId
    JOIN
        DB1.dbo.PatientProfile PP On PP.PatientProfileId = PatIns.PatientProfileId 
    LEFT OUTER JOIN 
        DB1.dbo.Guarantor G ON PatIns.PatientProfileId = G.PatientProfileId
    JOIN 
        Warehouse.dbo.InsuranceSubscriber InsSub ON InsSub.InsuranceCarriersID = PatIns.InsuranceCarriersId 
                        AND InsSub.OrderForClaims = PatIns.OrderForClaims
                        AND ((InsSub.GuarantorID = G.GuarantorId) OR (InsSub.GuarantorID IS NULL AND G.GuarantorId IS NULL)) 
    JOIN 
        Warehouse.dbo.Encounter E ON E.PatientEncounterID = PV.PatientVisitId      

执行计划规定有

哈希匹配右外部联接，成本为89%

查询的最后一步

查询中没有正确的外部联接，因此我看不出问题出在哪里

如何使查询更高效

以下是哈希映射的详细信息：

---

我会根据减少每个联接返回的记录数的能力对联接重新排序。无论哪种联接可以减少返回的数量或记录，都将提高效率。然后执行外部联接。此外，表锁定总是一个问题，因此添加withnolock以防止记录被锁定

也许像这样的东西需要稍微调整一下

INSERT INTO SubscriberToEncounterMapping (
    PatientEncounterID
    , InsuranceSubscriberID
    )
SELECT PV.PatientVisitId AS PatientEncounterID
    , InsSub.InsuranceSubscriberID
FROM DB1.dbo.PatientVisit PV WITH (NOLOCK)
INNER JOIN Warehouse.dbo.Encounter E WITH (NOLOCK)
    ON E.PatientEncounterID = PV.PatientVisitId
INNER JOIN DB1.dbo.PatientVisitInsurance PVI WITH (NOLOCK)
    ON PV.PatientVisitId = PVI.PatientVisitId
INNER JOIN DB1.dbo.PatientInsurance PatIns WITH (NOLOCK)
    ON PatIns.PatientInsuranceId = PVI.PatientInsuranceId
INNER JOIN DB1.dbo.PatientProfile PP WITH (NOLOCK)
    ON PP.PatientProfileId = PatIns.PatientProfileId
INNER JOIN Warehouse.dbo.InsuranceSubscriber InsSub WITH (NOLOCK)
    ON InsSub.InsuranceCarriersID = PatIns.InsuranceCarriersId
        AND InsSub.OrderForClaims = PatIns.OrderForClaims
LEFT JOIN DB1.dbo.Guarantor G WITH (NOLOCK)
    ON PatIns.PatientProfileId = G.PatientProfileId
        AND (
            (InsSub.GuarantorID = G.GuarantorId)
            OR (
                InsSub.GuarantorID IS NULL
                AND G.GuarantorId IS NULL
                )
            )

---

为了详细说明我的评论，您可以尝试将其分为两个查询，第一个查询在GuarantorID上匹配，第二个查询在InsuranceSubscriber中为空时匹配，第二个查询在AssuranceSubscriber中匹配，或者如果Guaranter中的记录完全缺失：

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首先：我在您的语句中没有看到任何表使用您在列的SELECT列表中使用的InsSub别名。。。。。另外：您真的需要连接所有这些表来获得这两条信息吗？您能显示哈希匹配的详细信息吗？什么是探头，什么是输出？从屏幕截图上看不清楚。我猜想这个谓词会导致你的问题--Sub.GuangthRoID.G.CuaAutoRID或SuS.CuavangRoID为null，G.CuaAutoRID为NULL，你可能希望考虑使用两个查询，并将结果联合在一起，通常当你有或这样的谓词导致一个次优的计划时，这两个独立的查询能够更好地利用索引。@GarethD可能在where子句中使用EXISTS，而不是在join中使用这两个谓词？是的。我需要那些连接。InsSub别名用于获取插入的保险订户ID。添加NOLOCK对执行计划中的哈希联接运算符有何影响？除非使用选项FORCEORDER，否则写入联接的顺序与执行联接的顺序无关，因此这没有任何区别。您可能还希望阅读，这不是一个神奇的性能修复程序，应该谨慎使用，通常是那些理解并意识到风险的人。我发现连接顺序确实很重要，如果您希望信任优化器为连接执行它的工作，那么这很好，或者您可以自己进行优化。同意无锁可能不需要或不理想，但如果某个东西正在锁定，它将通过防止等待锁来加快执行速度。如果它不能帮助移除它们。哈希匹配将始终存在，但在操作中减少记录集大小应该会有所帮助。这肯定会快很多！但返回的记录与原始查询不同。所以我得走了，但这绝对是我要走的路！。谢谢

INSERT INTO SubscriberToEncounterMapping(PatientEncounterID, InsuranceSubscriberID)
SELECT  PV.PatientVisitId AS PatientEncounterID, InsSub.InsuranceSubscriberID 
FROM    DB1.dbo.PatientVisit PV 
        JOIN DB1.dbo.PatientVisitInsurance PVI 
            ON PV.PatientVisitId = PVI.PatientVisitId
        JOIN DB1.dbo.PatientInsurance PatIns 
            ON PatIns.PatientInsuranceId = PVI.PatientInsuranceId
        JOIN DB1.dbo.PatientProfile PP 
            ON PP.PatientProfileId = PatIns.PatientProfileId 
        JOIN DB1.dbo.Guarantor G 
            ON PatIns.PatientProfileId = G.PatientProfileId
        JOIN  Warehouse.dbo.InsuranceSubscriber InsSub
            ON InsSub.InsuranceCarriersID = PatIns.InsuranceCarriersId 
            AND InsSub.OrderForClaims = PatIns.OrderForClaims
            AND InsSub.GuarantorID = G.GuarantorId
        JOIN Warehouse.dbo.Encounter E 
            ON E.PatientEncounterID = PV.PatientVisitId  
UNION ALL
SELECT  PV.PatientVisitId AS PatientEncounterID, InsSub.InsuranceSubscriberID 
FROM    DB1.dbo.PatientVisit PV 
        JOIN DB1.dbo.PatientVisitInsurance PVI 
            ON PV.PatientVisitId = PVI.PatientVisitId
        JOIN DB1.dbo.PatientInsurance PatIns 
            ON PatIns.PatientInsuranceId = PVI.PatientInsuranceId
        JOIN DB1.dbo.PatientProfile PP 
            ON PP.PatientProfileId = PatIns.PatientProfileId 
        JOIN  Warehouse.dbo.InsuranceSubscriber InsSub
            ON InsSub.InsuranceCarriersID = PatIns.InsuranceCarriersId 
            AND InsSub.OrderForClaims = PatIns.OrderForClaims
            AND InsSub.GuarantorID IS NULL
        JOIN Warehouse.dbo.Encounter E 
            ON E.PatientEncounterID = PV.PatientVisitId  
WHERE   NOT EXISTS
        (   SELECT  1
            FROM    DB1.dbo.Guarantor G 
            WHERE   PatIns.PatientProfileId = G.PatientProfileId
            AND     InsSub.GuarantorID IS NOT NULL
        );