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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

  • Understanding Columnstore Indexes in SQL Server Part 1
    Understanding Columnstore Indexes in SQL Server Part 1
  • SQL Index Creation Using DROP EXISTING= ON
    SQL Index Creation Using DROP EXISTING= ON
  • It's All in the Name, Index Naming Conventions
    It's All in the Name, Index Naming Conventions
  • Resizing Tempdb (When TEMPDB Wont Shrink)
    Resizing Tempdb (When TEMPDB Wont Shrink)
  • Memory Optimized Tables in SQL Server
    Memory Optimized Tables in SQL Server
  • Add Azure Cache for Redis to Your Azure SQL Performance Tuning Toolbox
    Add Azure Cache for Redis to Your Azure SQL Performance Tuning Toolbox
  • The Case of the Forgotten Compatibility Mode -  Scooby Dooing Episode 3
    The Case of the Forgotten Compatibility Mode - Scooby Dooing Episode 3
  • Filtered Index Basics
    Filtered Index Basics
  • Hide and Group Columns in SSRS Using a Parameter
    Hide and Group Columns in SSRS Using a Parameter
  • VLFs the Forgotten Foe
    VLFs the Forgotten Foe
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