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13 Things You Should Know About Statistics and the Query Optimizer

Fabiano launches into a sound technical explanation of the way that the query optimiser works in SQL Server with a mention of Brazilian Soccer stars and young ladies on Copacabana beach. You'll never quite think of statistics, execution plans, and the query optimiser the same way again after reading this, but we think you'll understand them better.  Read more...
By Additional Articles 2010/02/02 | Source: SimpleTalk | Category: statistics
Rating:  Rate this |   Briefcase | 5,453 reads

Index Primer - Just what statistics are kept?

An in-depth look at index statistics and how they are used by the optimizer by Josef Richberg.   Read more...
By Josef Richberg 2009/10/28 | Source: SQLServerCentral.com | Category: optimizer
Rating: |  Discuss |   Briefcase | 7,596 reads

Collecting Query Statistics for SQL Server 2005

With SQL Server 2005 DMVs, we can easily find query performance statistics. Every DBA has a favorite script to find query performance stats. I also have one. But, are all the queries captured by the DMVs? In this tip I will walk through capturing some of this data and show what is capture and what is not captured by the DMVs.  Read more...
By Additional Articles 2009/10/05 | Source: MSSQLTips.com | Category: statistics
Rating:  Rate this |   Briefcase | 4,339 reads

Statistics Used by the Query Optimizer in Microsoft SQL Server 2008

Microsoft SQL Server 2008 collects statistical information about indexes and column data stored in the database. These statistics are used by the SQL Server query optimizer to choose the most efficient plan for retrieving or updating data. This paper describes what data is collected, where it is stored, and which commands create, update, and delete statistics. By default, SQL Server 2008 also creates and updates statistics automatically, when such an operation is considered to be useful. This paper also outlines how these defaults can be changed on different levels (column, table, and database).  Read more...
By Additional Articles 2009/07/24 | Source: TechNet Blogs | Category: query optimization
Rating: (not yet rated)  Rate this |   Briefcase | 2,107 reads

Retaining historical index usage statistics for SQL Server - Part 2

We look at performing the same task for the sys.dm_db_index_operational_stats Dynamic Management Function (or DMF.) The process is identical, the code is however quite different due to the structural differences between sys.dm_db_index_usage_stats and sys.dm_db_index_operational_stats.  Read more...
By Additional Articles 2009/06/24 | Source: MSSQLTips.com
Rating: (not yet rated)  Rate this |   Briefcase | 2,017 reads

Retaining historical index usage statistics for SQL Server

In this three-part series I'll look at what you can do to persist this data so you don't find yourself waiting for usage stats to compile over a reasonable period of time just so you can harness the power of the indexing DMOs in your performance tuning process.   Read more...
By Additional Articles 2009/05/26 | Source: MSSQLTips.com | Category: statistics
Rating: (not yet rated)  Rate this |   Briefcase | 929 reads

Index Metadata and Statistics Update Date for SQL Server

Statistics update date is stored as metadata on the SQL instance, but after a great deal of research against the system tables and DMVs I realized that this information is not readily exposed to the DBA via any other method than the STATS_DATE() function or the SQL Server Management Studio graphical user interface (GUI).  Read more...
By Additional Articles 2008/08/12 | Source: MSSQLTips.com | Category: indexing
Rating: (not yet rated)  Rate this |   Briefcase | 2,492 reads

Rebuilding Stats: Twice or Not At All

Are you rebuilding statistics twice on your tables? Longtime expert, Andy Warren, shows why you might be asking more work of your SQL Server than is required.  Read more...
By Andy Warren 2008/07/29 | Source: SQLServerCentral.com | Category: indexing
Rating: |  Discuss |   Briefcase | 8,899 reads

Statistics and Indexes

When is it okay to let SQL Server to make a statistic for columns in your queries, and when should you take those statistics and make an index out of them? What I do is to test all of my procs, and if they generate system statistics (_WA_SYS%), then I add an index to the table for the column in the statistic. But is this a good practice?  Read more...
By Additional Articles 2008/03/11 | Source: SQL Community | Category: indexing
Rating:  Rate this |   Briefcase | 3,285 reads
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