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• Internals
• Joins
• Partitioning
• Performance
• Query Plans
• Seeks
• Undocumented

• Why Doesn’t Partition Elimination Work?

  Given a partitioned table and a simple SELECT query that compares the partitioning column to a single literal value, why does SQL Server read all the partitions when it seems obvious that only one partition needs to be examined? Sample Data The following Read More... Posted Wednesday, September 12, 2012 10:52 AM by Paul White | 14 Comments Filed under: Query Plans, Performance, Conversions, Partitioning

• Dynamic Seeks and Hidden Implicit Conversions

  Most people know that a LIKE predicate with only a trailing wildcard can usually use an index seek: SELECT p.Name FROM Production.Product AS p WHERE p.Name LIKE N 'D%' ; As the execution plan shows, SQL Server determines a covering range (which depends Read More... Posted Wednesday, January 18, 2012 2:37 AM by Paul White | 18 Comments Filed under: Seeks, Performance, Conversions

• Join Performance, Implicit Conversions, and Residuals

  You probably already know that it’s important to be aware of data types when writing queries, and that implicit conversions between types can lead to poor query performance.  Some people have gone so far as to write scripts to search the plan cache Read More... Posted Tuesday, July 19, 2011 1:17 AM by Paul White | 16 Comments Filed under: Internals, Query Plans, Undocumented, Performance, Joins, Conversions