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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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Monica Morehouse (Rathbun)

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

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Top Posts & Pages

  • Memory Optimized Tables in SQL Server
    Memory Optimized Tables in SQL Server
  • What’s a Key Lookup?
    What’s a Key Lookup?
  • Hide and Group Columns in SSRS Using a Parameter
    Hide and Group Columns in SSRS Using a Parameter
  • Please Don’t Do This! Default Index Fill Factor
    Please Don’t Do This! Default Index Fill Factor
  • SQL Index Creation Using DROP EXISTING= ON
    SQL Index Creation Using DROP EXISTING= ON
  • Summit Submission Feedback Response
    Summit Submission Feedback Response
  • Understanding Columnstore Indexes in SQL Server Part 3
    Understanding Columnstore Indexes in SQL Server Part 3
  • Expanding My Reach
    Expanding My Reach
  • SQL Server Data Collection and Management Data Warehouse
    SQL Server Data Collection and Management Data Warehouse
  • How Much Will Compression Really Gain Me in SQL Server?
    How Much Will Compression Really Gain Me in SQL Server?
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