sql-server – 这个NO JOIN PREDICATE告诫我应该感想鉴戒吗？

我正在对一本机能不佳的存储进程的各个部门举办妨碍解除.该措施的这一部门是抛出NO JOIN PREDICATE告诫

select
    method = 
        case methoddescription 
            when 'blah' then 'Ethylene Oxide'
            when NULL then 'N/A'
            else methoddescription
        end,testmethod = 
        case methoddescription 
            when 'blah' then 'Biological Indicators'
            when NULL then 'N/A'
            else 'Dosimeter Reports'
        end,result = 
        case when l.res is null or l.res <> 1 then 'Failed'
        else 'Passed'
        end,datecomplete = COALESCE(CONVERT(varchar(10),NULL,101),'N/A')
from db2.dbo.view ls
    join db1.dbo.table l
        on ls.id = l.id
    where item = '19003'
        and l.id = '732820'

视图([ls])挪用长途处事器(打算右侧的长途查询A).

这是该打算的图像：

由于this blog post我只问这个题目并且我想确保往后再也不会再咬我了.

办理要领

即

FROM   db2.dbo.VIEW ls
       JOIN db1.dbo.table l
         ON ls.id = l.id
WHERE  l.id = '732820'

是沟通的

( /*...*/ FROM   db2.dbo.VIEW ls WHERE id = '732820'  )
   CROSS JOIN 
  ( /*...*/  FROM   db1.dbo.table l WHERE id = '732820'  )

这次重写是not bad for performance.

This derivation is a good thing. It allows SQL Server to filter out rows … earlier than would otherwise be possible.

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