If the number of distinct values of a column is less than 1% of the
number of rows in the table, or if the values in a column are repeated more than 100 times, then the column is a candidate for a bitmap index.
a bitmap index on this column can out-perform a b-tree
index, particularly when this column is often queried in conjunction with other columns.[@more@]
number of rows in the table, or if the values in a column are repeated more than 100 times, then the column is a candidate for a bitmap index.
a bitmap index on this column can out-perform a b-tree
index, particularly when this column is often queried in conjunction with other columns.[@more@]
来自 “ ITPUB博客 ” ，链接：https://blog.itpub.net/10599713/viewspace-966733/ ，如需转载，请注明出处，否则将追究法律责任。
上一篇：
login as sysdba
下一篇：
Sqlplus查询时不能显示标题栏
请登录后发表评论
登录
全部评论
-
博文量740
-
访问量2002853
最新文章
- 人力&人手&人才&人物
- oracle树中prior的用法
- Using Supplied Packages to Manage Stored Outlines
- $ORACLE_HOMERDBMSADMIN目录下各SQL的含义
- PRODUCT_USER_PROFILE Table
- Backing Up Server Parameter Files with RMAN
- Backing Up Control Files with RMAN
- Backing Up Individual Tablespaces with RMAN
- Making Whole Database Backups with RMAN
- 目睹奥运火炬传递
