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：
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) CPWHERE 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。。。
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：
/****** 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：
然后加入条件：
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。
嘿嘿，看来他们的查询效率是一样的。
but why????百度下吧。。。。
筑起梦想的鸟巢，开始人生的长跑，领先每回的冲刺，
