摘要
在 SQL Server 6 .5中 ,表扫描和索引访问是两种主要的数据检索方法 ,是否使用簇索引或非簇索引是检索性能重要的因素 ,检索结果返回行数占表总行数的百分比 (简称为返回百分比 )对检索性能也有很大的影响 .索引访问的性能并非总是优于表扫描 .事实上 ,选择检索方法的工作由查询优化器来完成 ,但查询优化器并非总能选择最快的方法 .
Table scan and index access is the two main method of data query in SQL Server 6.5. The important factor affecting query performance is whether you use a clustered or a nonclustered index. The percentage of rows returned is another factor in providing better query performance. The query performance of index access is not always better then that of table scan. The fact, the query optimizer chooses the query method, but it doesnt always choose the fastest method.
出处
《小型微型计算机系统》
CSCD
北大核心
2001年第9期1144-1146,共3页
Journal of Chinese Computer Systems
关键词
数据库
SQLServer6.5
表扫描
索引访问
Query performance
Table scan
Clustered index access
Nonclustered index access
Query optimizer
The percentage of rows returned
