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  • Back to Basics,  Performance Tuning

    What’s a Key Lookup?

    April 3, 2019 /

    One of the easiest things to fix when performance tuning queries are Key Lookups or RID Lookups. The key lookup operator occurs when the query optimizer performs an index seek against a specific table and that index does not have all of the columns needed to fulfill the result set. SQL Server is forced to go back to the clustered index using the Primary Key and retrieve the remaining columns it needs to satisfy the request. A RID lookup is the same operation but is performed on a table with no clustered index, otherwise known as a heap.  It uses a row id instead of a primary key to do…

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    Monica Morehouse (Rathbun)

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About Me

Monica Morehouse (Rathbun)

Microsoft MVP, Performancing Tuning Expert, Leader Hampton Roads SQL Server User Group, Read More…

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Top Posts & Pages

  • What’s a Key Lookup?
    What’s a Key Lookup?
  • Does Your Code Have a Preamble?
    Does Your Code Have a Preamble?
  • Summit Submission Feedback Response
    Summit Submission Feedback Response
  • Run Book, Run!!!
    Run Book, Run!!!
  • Understanding Columnstore Indexes in SQL Server Part 1
    Understanding Columnstore Indexes in SQL Server Part 1
  • Memory Optimized Tables in SQL Server
    Memory Optimized Tables in SQL Server
  • It's All in the Name, Index Naming Conventions
    It's All in the Name, Index Naming Conventions
  • My Thoughts on PASS Virtual Summit – An Editorial
    My Thoughts on PASS Virtual Summit – An Editorial
  • The Shield
    The Shield
  • Maintaining Balance
    Maintaining Balance
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