SQL Server 中的覆盖索引和覆盖查询是什么?

What are Covering Indexes and Covered Queries in SQL Server?(SQL Server 中的覆盖索引和覆盖查询是什么?)

问题描述

你能解释一下微软 SQL Server 中 Covering Indexes 和 Covered Queries 的概念和关系吗?

Can you explain the concepts of, and relationship between, Covering Indexes and Covered Queries in Microsoft's SQL Server?

推荐答案

覆盖索引是一种可以满足查询中所有请求列的索引，而无需进一步查找聚集索引.

A covering index is one which can satisfy all requested columns in a query without performing a further lookup into the clustered index.

没有覆盖查询这样的东西.

There is no such thing as a covering query.

看看这篇 Simple-Talk 文章:使用覆盖索引提高查询性能.

Have a look at this Simple-Talk article: Using Covering Indexes to Improve Query Performance.

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