Articles tagged

Execution Plans Part 11: Actuals

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

Managing SQL Server Statistics

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

Statistics in SQL Server

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 If the statistics are wrong, outdated or missing then you have little realistic hope of having queries that perform well.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

Going Beyond the Relational Model with Data

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