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Indexes and Keys (197)

原创 数据库开发技术 作者:tsinglee 时间:2007-11-14 10:04:58 0 删除 编辑

Although the terms are often used interchangeably, indexes and keys are different.
Indexes are structures actually stored in the database, which users create, alter, and
drop using SQL statements. You create an index to provide a fast access path to table
data. Keys are strictly a logical concept. Keys correspond to another feature of Oracle
called integrity constraints, which enforce the business rules of a database.

Because Oracle uses indexes to enforce some integrity constraints, the terms key and
index are often are used interchangeably. However, do not confuse them with each
other.

索引与键
1. 索引是在数据库中实际存储的数据结构,用户可以使用 SQL 语句对其进行创建,修改,或移除.
索引提供了一种快速访问表数据的途径.
2. 键只是一个逻辑概念.键的概念主要在 Oracle 的完整性约束功能中使用.

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