d5da3f17   
   From: esquel@sommarskog.se   
      
   jbdhl (jbirksdahl@gmail.com) writes:   
   > Will the projection ever happen directly in the access method that   
   > fetch rows from the buffer? Or will it always be done at some point   
   > after the initial fetch?   
      
   I'm not sure that your question even does make sense. SQL Server reads   
   rows from pages, either from disk or from the buffer cache. When a plan   
   operator reads a row, it will read the columns that the parent operator   
   asks for. These columns can be in the SELECT list, or be needed for a   
   join elsewhere in the plan.   
      
   I would suggest that you study some query plans in SQL Server Management   
   Studio. This may not answer all your questions, but rather it may raise   
   new questions, but hopefully questions that are more on the mark.   
      
   --   
   Erland Sommarskog, SQL Server MVP, esquel@sommarskog.se   
      
   Links for SQL Server Books Online:   
   SQL 2008: http://msdn.microsoft.com/en-us/sqlserver/cc514207.aspx   
   SQL 2005: http://msdn.microsoft.com/en-us/sqlserver/bb895970.aspx   
   SQL 2000: http://www.microsoft.com/sql/prodinfo/previousversions/books.mspx   
      
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