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今天用sql profiler跟一个底层生成的SQL 的时候，跟到这样一段代码：
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WITH TempQuery AS
(
SELECT *, ROW_NUMBER() OVER (ORDER BY CreateTime DESC) AS 'RowNumberForSplit'
FROM (select E.Name as Name, U.RealyName as RealyName,C.[Description] as Descriptions,'求职者' as tsf ,C.Result,C.CreateTime from [Mr].[User_Complaint] UC inner join [Mr].[User] U on UC.UserCode=U.Code inner join [Mr].[Complaint] C on UC.ComplaintCode=C.Code inner join [Mr].[Enterprise] E on UC.EnterpriseCode=E.Code union select E.Name as Name, U.RealyName as RealyName,C.[Description] as Descriptions,'企业' as tsf ,C.Result,C.CreateTime from [Mr].[Enterprise_Complaint] EC inner join [Mr].[Enterprise] E on EC.EnterpriseCode=E.Code inner join [Mr].[Complaint] C on EC.ComplaintCode =C.Code inner join [Mr].[User] U on EC.UserCode=U.Code) CP
WHERE 1 = 1 AND 1=1
)
SELECT *
FROM TempQuery
WHERE RowNumberForSplit BETWEEN 1 AND 10;
SELECT COUNT(1) AS TOTAL_COUNT FROM (select E.Name as Name, U.RealyName as RealyName,C.[Description] as Descriptions,'求职者' as tsf ,C.Result,C.CreateTime from [Mr].[User_Complaint] UC inner join [Mr].[User] U on UC.UserCode=U.Code inner join [Mr].[Complaint] C on UC.ComplaintCode=C.Code inner join [Mr].[Enterprise] E on UC.EnterpriseCode=E.Code union select E.Name as Name, U.RealyName as RealyName,C.[Description] as Descriptions,'企业' as tsf ,C.Result,C.CreateTime from [Mr].[Enterprise_Complaint] EC inner join [Mr].[Enterprise] E on EC.EnterpriseCode=E.Code inner join [Mr].[Complaint] C on EC.ComplaintCode =C.Code inner join [Mr].[User] U on EC.UserCode=U.Code) CP WHERE 1 = 1 AND 1=1
然后你就看到后面跟着的where 1=1 and 1=1,以前也用过这个东西拼过条件，但是后来有人说这样影响查询性能，再后来又有人说不影响。然后我就迷茫了。。。
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还是自己做个实验测试下吧。
首先，先看一下没有这个条件的查询：
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/****** Script for SelectTopNRows command from SSMS ******/
SELECT TOP 100000 [RESOURCE_ID]
,[CLASS]
,[SORT_ID]
,[XML_CONTENT]
,[SEARCH_CONTENT]
,[ROW_ID]
FROM [MCS_WORKFLOW].[WF].[GENERIC_FORM_RELATIVE_DATA] WHERE 1=1 AND 1=1
然后使用执行计划来估计下：
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然后加入条件：
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在执行计划中可以看到，开销几乎全部在聚集索引表的扫描上，对比上图，发现这两张表数据一致。
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嘿嘿，看来他们的查询效率是一样的。