聚簇索引在数据库查询中的重要作用

本文从数据库查询优化角度，把数据库查３种常规操作细分，进而概括出几乎所有的查询算法都是这些操作的不同组合。然后列举出４种常见的连接查询方法，利用细分的操作为４种查询方法建立模型，量化和分析它们的一些关键参数，从而说明逻辑邻接项的物理聚簇索引会对数据库查询性能产生很大影响。索引对查询性能提高程度的关键取决于是否建立的是聚簇索引。

Cluster Index Plays an Important Role in Database Query

This paper from the point of database query optimization describes that there are three basic operation involving in database query, i.e. restriction, projection, join. Different query algorithms correspond to different sequences and methods of executing these operations on the two relations involved. Four methods for a general relational query that involves the operations are compared numerically and analytically for various situations. Results indicate that an index in evaluating a query depends on whether the relation is clustered or unclustered with related to the index. [