多关系SQL查询中连接顺序的优化  

Join Order Optimization in Multi-Relation SQL Query

作　　者：李桂杰[1] 梅红[2] 

机构地区：[1]杭州电子科技大学计算机学院,浙江杭州310018 [2]杭州电子科技大学理学院,浙江杭州310018

出　　处：《杭州电子科技大学学报（自然科学版）》2006年第2期31-34,共4页Journal of Hangzhou Dianzi University：Natural Sciences

摘　　要：关系数据库优化器确定SQL查询的执行计划是一个非常复杂的过程,该文概要性地介绍了数据库应用系统开发各个阶段的优化,对优化器的结构和优化方法作了陈述,包括SQL语句执行计划的产生和确定。该文只对SQL查询执行计划的表达和算法进行了介绍。同一SQL语句有多种执行计划,它们的结果相同,但代价相差巨大。优化的内容很多,包括连接算法的优化,连接顺序的优化,语义的优化,索引的优化等,阐述了Oracle数据库中多关系连接运算中连接顺序的优化方法,并给出了实际应用案例。The way of relational database optimizer to determine execution plans of SQL query is very complicated. This paper briefly introduces how each stag in developing management information system is optimized; organization of optimizer and its optimization strategy are also described including how the execution plans of SQL query are available. There are several executing ways or execution plans for one SQL statement, which can get the same result, but the efficiency is far more different. Limited to pages number, only expression of SQL query and algorithm for generating the execution plans are presented. Optimization includes join algorithm optimlzation,join order optimization, semantic optimization, index optimization and so on. But in this paper ,we emphasis on join order optimization and a case about multi - relation join order optimization based on Oracle is given.

关 键 词：查询优化 连接运算 关系数据库 

分 类 号：TP319[自动化与计算机技术—计算机软件与理论]