OQL逻辑优化准则  

OQL Logical Optimization Rules

作　　者：钟武[1] 胡守仁[1] 

机构地区：[1]国防科学技术大学计算机系,长沙410073

出　　处：《计算机科学》1998年第2期70-72,共3页Computer Science

摘　　要：对数据库查询的响应时间是数据库性能的重要指标。降低查询时间的关键是降低查询计算代价。因,查询优化的研究工作分两个方向展开：一是代价估算模型的研究；二是优化手段的研究。Rewrite the formula,which is equivalent to the semantic of query sentence with form of select-from-where,by means of some optimizing rules. The final formula rewrited in terms of these rules possesses following characteristic:during the term of running,it can dynamically select the optimum loop nesting relation and corresponding form of the moving-out of loop invariants with computed result of atomic predicate to accomplish OQL queries.

关 键 词：数据库 查询 OQL 逻辑优化准则 

分 类 号：TP311.13[自动化与计算机技术—计算机软件与理论]