Question

我正在调整存储过程的性能，而SQL Enlight正在抛出一个很高的阈值，并且猜测是因为有很多自连接。有没有其他方法可以重写自联接？

这是我正在使用的代码。

提前致谢。

    SELECT x.ClientName
    ,x.Category
    ,x.vchSSNumber
    ,x.dtDateOfBirth
    ,x.CYC0
    ,x.Total0
    ,Limit0 = CASE 
        WHEN x.category = 'IRA'
            THEN i0.mLimit
        WHEN x.category = 'Simple'
            THEN s0.mLimit
        ELSE NULL
        END
    ,Balance0 = CASE 
        WHEN x.category = 'IRA'
            THEN CASE 
                    WHEN i0.mLimit > 0
                        THEN i0.mLimit - x.Total0
                    END
        WHEN x.category = 'Simple'
            THEN CASE 
                    WHEN s0.mLimit > 0
                        THEN s0.mLimit - x.Total0
                    END
        ELSE NULL
        END
    ,x.CYC1
    ,x.PYC1
    ,x.Total1
    ,i1.mLimit AS Limit1
    ,Balance1 = CASE 
        WHEN i1.mLimit > 0
            THEN i1.mLimit - x.Total1
        END
    ,x.CYC2
    ,x.PYC2
    ,x.Total2
    ,i2.mLimit AS Limit2
    ,Balance2 = CASE 
        WHEN i2.mLimit > 2
            THEN i2.mLimit - x.Total2
        END
    ,Over70AndHalf = CASE 
        WHEN x.dtDateOfBirth < @year70
            THEN 1
        ELSE 0
        END
FROM ClientInfo x
--Only get contribution limits for IRA Category. Have to get for each year
--IF DOB is NULL, Assume it is today. This makes them under 50 yrs old
LEFT JOIN dbo.IRAContributionLimits i0 WITH (NOLOCK) ON @year0 - DATEPART(yy, ISNULL(x.dtDateOfBirth, @date)) BETWEEN i0.iMinAge
        AND i0.iMaxAge
    AND i0.iYear = @year0
    AND i0.vchCategory = x.category
    AND x.category = 'IRA'
LEFT JOIN dbo.IRAContributionLimits i1 WITH (NOLOCK) ON @year1 - DATEPART(yy, ISNULL(x.dtDateOfBirth, @date)) BETWEEN i1.iMinAge
        AND i1.iMaxAge
    AND i1.iYear = @year1
    AND i1.vchCategory = x.category
    AND x.category = 'IRA'
LEFT JOIN dbo.IRAContributionLimits i2 WITH (NOLOCK) ON @year2 - DATEPART(yy, ISNULL(x.dtDateOfBirth, @date)) BETWEEN i2.iMinAge
        AND i2.iMaxAge
    AND i2.iYear = @year2
    AND i2.vchCategory = x.category
    AND x.category = 'IRA'
LEFT JOIN dbo.IRAContributionLimits s0 WITH (NOLOCK) ON @year0 - DATEPART(yy, ISNULL(x.dtDateOfBirth, @date)) BETWEEN s0.iMinAge
        AND s0.iMaxAge
    AND s0.iYear = @year0
    AND s0.vchCategory = x.category
    AND x.category = 'Simple'
ORDER BY x.ClientName
    ,x.category
    ,x.vchSSNumber;

Answer 1

根据我的经验，自联接不一定是导致性能问题的原因。

查看您的查询或任何有性能问题的查询，我看到的第一个地方是您的索引。

您的dbo.IRAContributionLimits表是否有iMinAge，iMaxAge，iYear和vchCategory的索引？

您的ClientInfo表是否有dtDateOfBirth和category的索引？

有没有替代重写自我加入？

1 个答案: