摘要
直方图是一种重要的数据查询工具.在数据库操作中查询操作需要进行代价估计,而操作代价的估计有多种方法.直方图估计法在所有估计法中是最容易使用和最容易维护的,它将关系中的全部元组进行归类设桶,对每个桶分别进行大小统计,继而求和,使代价统计值更接近于真实.结合实际课题应用,给出了将关系的连接转换为多种直方图的方法,以及如何利用直方图进行代价估计.
Histogram is a kind of important tool in data query. Cost estimation needed in query operation of database varies in methods, in which histogram is that is most convenient for use and maintenance. Histogram categorizes and sets barrels to all tuples in the relations, calculates the size respectively for each barrel, and then summarizes, thus making the price statistics closer to the real value. In application of the actual program, this research works out methods that convert the connection of the relations to a variety of histograms and ways to estimate the operation cost by using histograms.
出处
《计算机系统应用》
2012年第10期194-197,共4页
Computer Systems & Applications
基金
四川省高等学校重点科研项目(11ZA178)
关键词
直方图
代价估计
元组
等宽
数据连接
查询
histogram
cost estimation
tuple
equal width
data connection
query
