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  • 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
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