SQL 连接提示影响行数？

Question

我在 SQL 2016 SP2 上有一个 SQL 视图，它在没有谓词的情况下连接 14 个表。

                WHEN dsp.DimSourceSystemID=2 THEN edsp.CyberExposureGroup
                WHEN dsp.DimSourceSystemID=4 THEN vdsp.CyberExposureGroup
                ELSE 'Unknown' END AS CyberExposureGroup    
       FROM     dwh.DimPolicy dsp
                INNER JOIN Eclipse.DimPolicyExt edsp
                ON dsp.DimEclipsePolicyExtID = edsp.DimEclipsePolicyExtID
                INNER JOIN Velocity.DimPolicyExt vdsp
                ON dsp.DimVelocityPolicyExtID = vdsp.DimVelocityPolicyExtID
                INNER JOIN DWH.DimProgramme dp
                ON dsp.DimProgrammeID = dp.DimProgrammeID
                INNER JOIN DWH.DimPricingLeaderStatus dpls
                ON edsp.DimPricingLeaderStatusID = dpls.DimPricingLeaderStatusID
                INNER JOIN DWH.DimPlacingBasis dpb
                ON dsp.DimPlacingBasisID = dpb.DimPlacingBasisID
                INNER JOIN DWH.DimCoverageBasis dcb
                ON dsp.DimCoverageBasisID = dcb.DimCoverageBasisID
            --INNER JOIN DWH.DimNewRenewed dnr
            --  ON dsp.DimNewRenewedID = dnr.DimNewRenewedID
                INNER JOIN DWH.DimSubClass dsc
                ON edsp.DimSubClassID = dsc.DimSubClassID
                INNER JOIN DWH.DimStatsMinorClass dsminc
                ON edsp.DimStatsMinorClassID = dsminc.DimStatsMinorClassID
                INNER JOIN DWH.DimStatsMajorClass dsmajc
                ON edsp.DimStatsMajorClassID = dsmajc.DimStatsMajorClassID
                ----------------------R5--------------------------
                INNER JOIN DWH.DimCoverholder cv
                ON edsp.DimCoverholderID = cv.DimCoverholderID
            ----------------------R7--------------------------
                LEFT JOIN dwh.DimPlacingBasis MDPB
                ON MDPB.MasterDataPlacingBasis = edsp.MasterPlacingBasis
                INNER JOIN DWH.DimAssured da
                ON dsp.DimAssuredID = da.DimAssuredID
                --Underwriter Information R15
                INNER JOIN DWH.DimUnderwriter duw
                ON dsp.DimUnderwriterID = duw.DimUnderwriterID

我想使用循环连接提示，以便查询的并行度开销较小。

                WHEN dsp.DimSourceSystemID=2 THEN edsp.CyberExposureGroup
                WHEN dsp.DimSourceSystemID=4 THEN vdsp.CyberExposureGroup
                ELSE 'Unknown' END AS CyberExposureGroup    
       FROM     dwh.DimPolicy dsp
                INNER LOOP JOIN Eclipse.DimPolicyExt edsp
                ON dsp.DimEclipsePolicyExtID = edsp.DimEclipsePolicyExtID
                INNER LOOP JOIN Velocity.DimPolicyExt vdsp
                ON dsp.DimVelocityPolicyExtID = vdsp.DimVelocityPolicyExtID
                INNER LOOP JOIN DWH.DimProgramme dp
                ON dsp.DimProgrammeID = dp.DimProgrammeID
                INNER LOOP JOIN DWH.DimPricingLeaderStatus dpls
                ON edsp.DimPricingLeaderStatusID = dpls.DimPricingLeaderStatusID
                INNER LOOP JOIN DWH.DimPlacingBasis dpb
                ON dsp.DimPlacingBasisID = dpb.DimPlacingBasisID
                INNER LOOP JOIN DWH.DimCoverageBasis dcb
                ON dsp.DimCoverageBasisID = dcb.DimCoverageBasisID
            --INNER JOIN DWH.DimNewRenewed dnr
            --  ON dsp.DimNewRenewedID = dnr.DimNewRenewedID
                INNER LOOP JOIN DWH.DimSubClass dsc
                ON edsp.DimSubClassID = dsc.DimSubClassID
                INNER LOOP JOIN DWH.DimStatsMinorClass dsminc
                ON edsp.DimStatsMinorClassID = dsminc.DimStatsMinorClassID
                INNER LOOP JOIN DWH.DimStatsMajorClass dsmajc
                ON edsp.DimStatsMajorClassID = dsmajc.DimStatsMajorClassID
                ----------------------R5--------------------------
                INNER LOOP JOIN DWH.DimCoverholder cv
                ON edsp.DimCoverholderID = cv.DimCoverholderID
            ----------------------R7--------------------------
                LEFT LOOP JOIN dwh.DimPlacingBasis MDPB
                ON MDPB.MasterDataPlacingBasis = edsp.MasterPlacingBasis
                INNER LOOP JOIN DWH.DimAssured da
                ON dsp.DimAssuredID = da.DimAssuredID
                --Underwriter Information R15
                INNER LOOP JOIN DWH.DimUnderwriter duw
                ON dsp.DimUnderwriterID = duw.DimUnderwriterID

这行得通并且查询运行得更快，但代价是更多的 IO，但是令我惊讶的是，对于视图的两个不同版本，我得到的行数略有不同。 7,877,287 行对比 7,877,285 行。这是一个数据仓库，但没有插入操作。那么连接提示会影响总行数还是这可能是一个错误？

Answer 1

好的，我实际上已经弄清楚了问题所在 - 它是 SSMS 中的错误！我使用的是 SSMS 18.6，右下角显示的行数不正确。如果您实际查看结果选项卡中的行数，那么它们确实对应，也就是说连接提示没有区别，这是有道理的

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