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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
  • Trace Flags That Are Now Defaulted Behaviors in SQL Server
    Trace Flags That Are Now Defaulted Behaviors in SQL Server
  • What’s a Key Lookup?
    What’s a Key Lookup?
  • Resizing Tempdb (When TEMPDB Wont Shrink)
    Resizing Tempdb (When TEMPDB Wont Shrink)
  • It's All in the Name, Index Naming Conventions
    It's All in the Name, Index Naming Conventions
  • Tempdb Performance Improvements in SQL Server 2022 are Dramatic
    Tempdb Performance Improvements in SQL Server 2022 are Dramatic
  • What Are These Backup Settings All About?
    What Are These Backup Settings All About?
  • The Case for Scooby-Dooing: Solving SQL Server Mysteries Like a Pro– Scooby Dooing Episode 8
    The Case for Scooby-Dooing: Solving SQL Server Mysteries Like a Pro– Scooby Dooing Episode 8
  • Scooby Dooing Episode 9: The Case of the Artificially Intelligent Villain
    Scooby Dooing Episode 9: The Case of the Artificially Intelligent Villain
  • What is Automatic Tuning in Azure SQL Database
    What is Automatic Tuning in Azure SQL Database
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