Truncate table updating statistics

21-Jun-2018 20:37 by 7 Comments

Truncate table updating statistics - does consolidating debt affect your credit score

The actual percentage or number of rows the query optimizer samples might not match the percentage or number specified.

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Transact-SQL Syntax Conventions is not specified, the query optimizer updates all statistics for the table or indexed view.The usual approach would be a weekly maintenance job.Then you could either wait for the job to run, or update the statistics manually.The engine would look at statistics to make the plan.It will see that the carefully crafted plan is 'meaningless' only when it actually tries to run it and ... So statistics are very important to an empty table: is the statistics that tell optimizer that the table is empty.Update all existing statistics, statistics created on one or more columns, or statistics created for indexes.

If none of the options are specified, the UPDATE STATISTICS statement updates all statistics on the table or indexed view.

The original answer was "Yes" because it's not automatic as part of TRUNCATE.

From "Index Statistics" in BOL IF OBJECT_ID('dbo.foo') IS NOT NULL DROP TABLE CREATE TABLE ( bar int NOT NULL IDENTITY (1, 1) PRIMARY KEY, thing int NOT NULL ) CREATE INDEX IX_thing ON (thing) INSERT (thing) SELECT c1.object_id FROM sys.columns c1, sys.columns c2 SELECT name AS index_name, STATS_DATE(object_id, index_id) AS After Load FROM sys.indexes WHERE object_id = OBJECT_ID('dbo.foo') SELECT DISTINCT thing FROM ORDER BY thing DESC SELECT name AS index_name, STATS_DATE(object_id, index_id) AS After First Query FROM sys.indexes WHERE object_id = OBJECT_ID('dbo.foo') DELETE TOP (50000) SELECT name AS index_name, STATS_DATE(object_id, index_id) AS After Delete FROM sys.indexes WHERE object_id = OBJECT_ID('dbo.foo') SELECT DISTINCT thing FROM ORDER BY thing DESC SELECT name AS index_name, STATS_DATE(object_id, index_id) AS After2nd Query FROM sys.indexes WHERE object_id = OBJECT_ID('dbo.foo') TRUNCATE TABLE SELECT name AS index_name, STATS_DATE(object_id, index_id) AS After Truncate FROM sys.indexes WHERE object_id = OBJECT_ID('dbo.foo') SELECT DISTINCT thing FROM ORDER BY thing DESC SELECT name AS index_name, STATS_DATE(object_id, index_id) AS After3rd Query FROM sys.indexes WHERE object_id = OBJECT_ID('dbo.foo') It depends on how your administrator has configured statistics.

Met à jour les statistiques d'optimisation de requête d'une table ou d'une vue indexée.

Par défaut, l'optimiseur de requête met à jour les statistiques en fonction des besoins afin d'améliorer le plan de requête ; dans certains cas, vous pouvez optimiser les performances des requêtes en utilisant UPDATE STATISTICS ou la procédure stockée sp_updatestats pour mettre à jour les statistiques de manière plus fréquente qu'avec les mises à jour par défaut.

SAMPLE is useful for special cases in which the query plan, based on default sampling, is not optimal.