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  • SQL TuneIn Zagreb 2014 – Session material

    I spent the last few days in Zagreb, Croatie, at the third edition of the SQL TuneIn conference, and I had a very good time here. Nice company, good sessions, and awesome audiences. I presented my “Understanding Execution Plans” precon to a small but interested audience on Monday. Participants have received a download link for the slide deck. On ...
  • Fake statistics, and how to get rid of them

    There are two ways to test how your queries behave on huge amounts of data. The simple option is to actually use them on huge amounts of data – but where do you get that if you have no access to the production database, and how do you store it if you happen not to have a multi-terabyte storage array sitting in your basement? So here’s the second ...
  • Stats on Stats

    I have been working on new features for the Rules-Driven Maintenance Solution, including per-index maintenance preferences and more selective processing for statistics. SQL Server stats is a topic I knew about at a high level, but lately I have had to take a deeper dive into the DMVs and system views and wrap my head around things like ...
    Posted to Merrill Aldrich (Weblog) by merrillaldrich on September 18, 2013
  • Fooling the Query Optimizer

    Did you ever wanted to know which execution plans the Query Optimizer would generate for your queries should your tables have millions of records? You can actually generate those plans by using the undocumented ROWCOUNT and PAGECOUNT options of the UPDATE STATISTICS statement. These options can be used on small or empty tables and can be ...
    Posted to Benjamin Nevarez (Weblog) by Ben Nevarez on January 13, 2010
  • For want of a nail

    For want of a nail the shoe was lost. For want of a shoe the horse was lost. For want of a horse the rider was lost. For want of a rider the battle was lost. For want of a battle the kingdom was lost. And all for the want of a horseshoe nail.   I'm now in the middle of severity A case that is best depicted by this ...
    Posted to Michael Zilberstein (Weblog) by mz1313 on December 7, 2009
  • Rebuilding Indexes vs. Updating Statistics

    One of the questions I was asked recently while speaking at user groups, was regarding the order that jobs like rebuilding indexes or updating statistics should be performed as part of the database maintenance activities. Then I started writing this post about this topic on the weekend but was interrupted several times, including one of them to ...
    Posted to Benjamin Nevarez (Weblog) by Ben Nevarez on October 6, 2009
  • How the Query Optimizer Uses Statistics

      This post shows how the Query Optimizer uses statistics to estimate the selectivity of expressions during query optimization.   You can also use this as a second part of my last post, The Query Optimizer and Parameter Sniffing. Here I will show you the advantage of the use of statistics when the Query Optimizer can “sniff” the ...
    Posted to Benjamin Nevarez (Weblog) by Ben Nevarez on September 3, 2009
  • The Query Optimizer and Parameter Sniffing

      As we all know, the SQL Server Query Optimizer uses statistics to estimate the cardinality and selectivity of predicates of a query to produce an optimal execution plan. The Query Optimizer accomplishes this by first inspecting the values of the query parameters. This behavior is called parameter sniffing and it is a good thing. Getting an ...
    Posted to Benjamin Nevarez (Weblog) by Ben Nevarez on August 27, 2009
  • The Query Optimizer and Computed Columns

    In my previous post I talked about contradiction detection as one of the early steps in query optimization. Another interesting step performed during query optimization is the automatic matching of computed columns. Although computed columns have been available in previous versions of SQL Server, the automatic matching feature was introduced until ...
    Posted to Benjamin Nevarez (Weblog) by Ben Nevarez on August 10, 2009
  • Lies, Damned Lies And Statistics – Part I

    One of the biggest call generators at Microsoft SQL Server Support when SQL Server 7.0 was released was issues with statistics. In the beginning, they tended to be about the Autoupdate statistics feature interfering with user activity but when SQL Server 2000 came, and systems running SQL Server became larger, issues with skewed statistics/data ...
    Posted to Elisabeth Redei (Weblog) by Elisabeth Redei on March 1, 2009
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