【摘要】 本文讨论了查询结果大小估计的主要方法，对直方图方法做了较详细的介绍，分析了查询结果大小估计误差的两种性能指标，给出了等宽直方图的描述．设计了用直方图估计选择运算与连接运算结果大小的算法，进行了相应的实验，并提出下一步工作的思路。更多还原

【Abstract】 This paper discusses several main methods of estimating the size of query result and introduces a method of histograms more detail. Two performance indexes of estimating error of the size of query results are analyzed. Description of an algorithm of Equal - width histograms is given. Algorithms of estimating the sizes of query results of selection operations and join operations are designed, and corresponding experiments are implemented, and a clue of further research is given.更多还原