在数据库中，键和索引之间有什么区别？ [英] In a database, what is the difference betwen a key and an index?

问题描述

例如，在SQLServer中，如果我有一个设置了unique的索引，那么这个不同于key的是什么？

For example, in SQLServer, if I have an index with 'unique' set on it, how is that different from a key?

我想使用键与索引字段？

How do I know when I want to use a Key vs. an Indexed field?

推荐答案

具有唯一值的字段基本上是一个键。但是，一个键用于唯一标识表中的行，而索引用于对表中的行进行排序或分组。一旦初始设置，密钥不应该更改，因为它可能在数据库中的其他地方引用。然而，索引字段可以自由更改。

An field which has unique values is, essentially, a key. However, a key is used to uniquely identify a row in a table, while an index is used to sort, or group, the rows in the table. A key should not change once it has been initially set, as it might be referenced to elsewhere in your database. An indexed field, however, can change freely.

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