Tips, Tricks, and Advice from the SQL Server Query Processing Team

The query processing team - query optimization & execution - providing tips, tricks, advice and answers to freqeuently-asked questions in a continued effort to make your queries run faster and smoother in SQL Server.

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  • Blog Post: Mystery of memory fraction in Showplan XML

    If you examine Showplan XML, you may find an entry like <MemoryFractions Input="1" Output="1" /> on some operators . They are internal parameters used by query memory grant to save overall memory usage, and “fraction” means how much this operator is allowed to use from “total additional memory...
  • Blog Post: How to Check Whether the Final Query Plan is Optimized for Star Join Queries?

    The star join optimization technique is an index based optimization designed for data warehousing scenarios to make optimal use of non-clustered indexes on the huge fact tables. The general idea is to use the non-clustered indexes on the fact table to limit the number of rows scanned from it. More details...
  • Blog Post: Showplan Trace Events

    Besides SSMS, another great tool available to database developers and DBAs to view query plans and troubleshoot query compilation or execution issues is the SQL Server Profiler. In the Profiler, all the showplan events are listed under the Performance Event category. All the SQL Trace events generate...
  • Blog Post: Viewing and Interpreting XML Showplans

    As mentioned in our previous blog posting, SQL Server 2005 supports Showplan generation in XML format. XML-based Showplans provide greater flexibility in viewing query plans and saving them to files as compared to legacy Showplans. In addition to the usability benefits, XML-based Showplans also contain...
  • Blog Post: Introduction to Showplan

    Showplan is a feature in SQL Server to display and read query plans. While some of you may already be very familiar with Showplan, it is one of the most important diagnostic tools that we use in the query processing team to locate and identify problems, and therefore deserves some extra exposure. Being...
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