concept---Index-Organized Table
1. Overview
A table stored in a variation of B-tree index structure.
Each index entry in the B-tree also stores non-key column values. Thus, the index is the data, the data is the index.
Faster access to table rows by primary key or a valid
prefix of the key.
Avoid an
additional data block I/O for the presence of non-key columns of a row in the leaf block.
2. Characteristics
- Primary key uniquely identifies a row.Primary key constraint must be defined. Unlike heap-organized table, the rowid uniquely identifies a row.
- Logical rowid in ROWID pseudocolumn allows building secondary indexes. In the heap-organized table, physical rowid in ROWID pseudocolumn allows building secondary indexes.
- Access to individual rows may be achieved indirectly by primary key.
- A full index scan or fast full index scan returns all rows in some order.
- Cannot be stored in a table cluster.
- Can contain LOB columns but not LONG columns.
- Cannot contain virtual columns.
3. Row Overflow Area
来自 “ ITPUB博客 ” ，链接：https://blog.itpub.net/26679417/viewspace-750163/ ，如需转载，请注明出处，否则将追究法律责任。
请登录后发表评论
登录
全部评论
