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  • SQL中使用WITH AS提高性能(二)

    继上一节

    对比两条查询,第一是用了with as 第二条语句没用with as 查看执行计划的效果

    WITH    vep
              AS ( SELECT   package.OrderCode ,
                            RANK() OVER ( PARTITION BY package.OrderCode ORDER BY package.ID ) AS Index ,
                            COUNT(1) OVER ( PARTITION BY package.OrderCode ) AS Count
                   FROM     dbo.BookPackages package WITH ( NOLOCK )
                 )
        SELECT TOP 100
                *
        FROM    vep
        WHERE   vep.Count > 2
    

      

    SELECT TOP 100 * FROM (
    SELECT 
    	vep.OrderCode,
    	ROW_NUMBER() OVER(PARTITION BY vep.OrderCode ORDER BY vep.ID ) 'Index',
    	COUNT(1) OVER(PARTITION BY vep.OrderCode) 'Count'
    FROM 
    	dbo.BookPackages 
    vep WITH(NOLOCK) ) a WHERE a.Count>2

      明显用了with as 快了很多

    中间用到了 rank() over (partition by over by) 语句,下一篇再写

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  • 原文地址:https://www.cnblogs.com/sheseido/p/3471419.html
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