数据仓库中的一种提高多表连接效率的有效方法

联机分析处理OLAP查询经常涉及多表连接，所以提高多表连接的性能就成了提高OLAP查询处理的关键性问题．针对目前直接提高多表连接效率的方法、并行多表连接算法和连接索引，提出了变形多表连接索引．该方法基于使用SQL语句表述的查询模型库QMB建立一系列符合条件的变形多表连接事实表，并建立这些变形多表连接事实表的索引．在特定的多表连接查询中，变形多表连接事实表能替代原事实表与各维表连接，并在查询处理过程中动态更新．理论分析和实验结果表明，该方法可以有效地提高多表连接的查询效率．

An Efficient Method for Multi-Table Joining in Data Warehouse

OLAP (online analytical processing) queries usually involve multi-table joining. As a result, how to improve the performance of multi-table joining becomes a key issue for OLAP query processing. A method of distortional multi-table joining index is proposed, which can achieve better performance on the aspect of multi-table joining than parallel multi-joining algorithm and joining index. Based on query model-base, in which queries are expressed in SQL, the algorithm is used to build a series of distortional multi-table joining fact tables and indexes of them. In particular queries, dimensional tables join with distortional multi-table joining fact tables instead of fact tables, and further more, distortional multi-join indexes can be dynamically updated in query processing. Theoretical analysis and experimental results show that distortional multi-table joining index is an efficient method for multi-table joining in data warehouse.