Auto-Create statistics is a well-known feature critical for the database performance. When one statistic is auto created, changing the table structure is not blocked by the presence of the statistic. An auto-created statistics is also dropped automatically when a schema change happens. On the other hand, if the statistic is created by the user, any … Read more
R and SQL Server are a match made in heaven. You don't need anything special to get started beyond the basic instructions. Once you have jumped the hurdle of reliably and quickly transferring data between R and SQL Server you are ready to discover the power of a relational database when when combined with statistical computing and graphics.… Read more
So far in this series we’ve talked about interpreting the shape of an execution plan and understanding the meaning of the predictions that the optimizer has made about cost and cardinality. It’s finally time to see how Oracle gives us execution plans that show us how well the optimizer’s estimates match the actual work done as the query ran. Ther… Read more
Following on from his first four articles on using Data Analysis Expressions (DAX) with tabular databases, Robert Sheldon dives into some of the DAX statistical functions available, demonstrating which are the most useful and examples of how they work. … Read more
Accurate statistics about the data held in tables are used to provide the best execution strategy for SQL queries. but if the statistics don't accurately reflect the current contents of the table you'll get a poorly-performing query. How do you find out if statistics are correct, and what can you do if the automatic update of statistics isn't right for the way a table is used? … Read more
When a database starts showing signs of an illness, it's up to the DBA to get to the root of the problem, fast. Kat Hicks takes a look at the most common causes of database troubles, free tools that can help, and the misconceptions that get in the way. … Read more
SQL Server's Query Optimiser relies on statistics for providing a decent query plan. If the statistics are wrong, outdated or missing then you have little realistic hope of having queries that perform well. It is therefore important to appreciate how SQL Server maintains distribution statistics.… Read more
SQL is a powerful tool for querying data, and for aggregating it. However, you can't easily use it to draw inferences, to make predictions, or to tease out subtle correlations. To provide ever more sophisticated inferences to businesses, the race is on to combine the power of the relational model with advanced statistical packages. Both IBM and PostGres are ready with solutions. And SQL Server? Hmm...… Read more
Fabiano was asked a couple of questions about SQL Server Distribution Statistics. Having given an answer based on his current knowledge, he then decided to find out for himself whether what he'd said was right, and started an epic journey of exploration into Distribution Statistics and the way that the Query Optimiser uses them.… Read more
SQL Server Statistics assist the query optimiser to calculate the best way of running the query. Holger describes every common way that things can go wrong with statistics, and how to put matters right.
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