Consistent query answering based on virtual repairs with nulls
基于空值修复的数据库一致性查询方法*

ntegrity constraints are used to define the data semantics in databases. The database instanced and the tuples violating the constraints were inconsistent. Consistent query answering was one technique to obtain consistent answer from inconsistent database. The applicable areas of current techniques were limited because they supported little types of constraints or their high computation complexity. This paper presented a new approach based on null repair. Transformed the constraints first to unified format to locate inconsistency, and then rewritten the original SQL queries to query consistent answers by treating inconsistent attributes as nulls. The implementation of the system and the experiment results show that this approach can achieve stable performance under multiple combinations of constraints and SQL queries.