什么是优化器统计信息？----系列二
----
系列二
block
db_file_multiblock_read_countuser_tab_statisticsNDV
user_tab_col_statisticssql10010
histogramcolumns groupsexpression statistics
histograms
num_rows
/num_distinctOracle
sys.col_usage$oracle2
frequencyheight-balancedOracle
254
oracleOracle
- oraclePROMOTIONSPROMO_CATEGORY_IDpromo_category_idpromo_category_id
- promo_category_id
- 254histogram bucketbucket
2bucket 115bucket 115bucket 484bucket
503bucket 503bucketsfigure 4dbms_stats
- promo_category_idpromo_category_id=10end point10bucketendpoint10bucket 503 bucket bucket 483503-483=20 : (number of bucket endpoints / total number of bucket) * NUM_ROWS , 20/503X 503 promotionspromo_category_id = 1020
本站文章为和通数据库网友分享或者投稿，欢迎任何形式的转载，但请务必注明出处.
同时文章内容如有侵犯了您的权益，请联系QQ：970679559，我们会在尽快处理。