SQL Server Statistics
What statistics are for?
Query processing phases
- Bullet One
- Bullet Two
- good enough execution plan
Cardinality estimation
- number of rows that need to be processed on each step of the query execution
- important factor in query optimization
- affects:
- choice of join strategies
- memory grants
What statistics are?
- system object
- contain the information about data distribution:
- in columns which comprise indices' keys
- sometimes in regular column values
- column data type has to support comparison operators
DBCC SHOW_STATISTICS
- returns three result sets
- general metadata information
- density
- histogram
- Bullet Two
- Bullet Three
deck
By rav
