Optimizer statistics are a collection of data that describe more details about the database and the objects in the database. These statistics are used by the query optimizer to choose the best execution plan for each SQL statement.
[@more@]Optimizer statistics include the following:
Table statistics
Number of rows
Number of blocks
Average row length
Column statistics
Number of distinct values (NDV) in column
Number of nulls in column
Data distribution (histogram)
Index statistics
Number of leaf blocks
Levels
Clustering factor
System statistics
I/O performance and utilization
CPU performance and utilization
注：042 TK 46题
来自 “ ITPUB博客 ” ，链接：https://blog.itpub.net/248644/viewspace-930290/ ，如需转载，请注明出处，否则将追究法律责任。
