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In the realm of SQL Server database management, Statistics is a fundamental feature that plays a key role in optimizing query performance. If your statistics are up-to-date, the SQL Server query optimizer can make better decisions on execution plans, potentially improving your overall query speed.
What are SQL Server Statistics?
SQL Server Statistics hold summary information about the data within a table or indexed views, which is used by the SQL Server optimizer to estimate the cost of retrieving or updating data when it creates query plans. They contain histogram of the column values, the count of rows and pages in a table and other related information.
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-- The below SQL statement updates the statistics of all tables of the current database: EXEC sp_updatestats; |
Types of SQL Server Statistics
There are two types of statistics: index and column statistics.
Index Statistics are generated by default when an index is created in a table. They provide distribution of values key columns in an index.
Column statistics, on the other hand, must be manually created. They provide distribution of values for one or more columns.
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-- To create column statistics use the CREATE STATISTICS statement: CREATE STATISTICS stats_name ON table_name(column_name); |
Updating SQL Server Statistics
SQL Server, by default, auto-updates statistics whenever it is necessary. However, depending on the volume of data changes, manual updates might be needed. Doing so provides the query optimizer with updated statistics helping it to create better execution plans.
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-- The below SQL statement updates the statistics of a specific table: UPDATE STATISTICS table_name; |
Conclusion
Working efficiently with SQL Server Statistics is essential for maintaining optimal database performance. By understanding what statistics are, their types, and the way they function, you can make informed decisions about when to update or modify them, resulting in improved query performance.
Remember, coding is a continuous journey and there’s always something new to learn and improve. Happy Coding!
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-- always keep improving SELECT * FROM continuous_learning; |