SQL Extension for Multidatabase System

The most important feature of a multidatabase system (MDBS) is to provide the global schema with integrating various models of local database systems (LDBS). However, it is difficult to integrate local schemas into the global schema due to the difference of the syntactical and semantic expressions of LDBSs. In this paper, we propose the standard SQL extension for MDBS called by Multidatabase Query Language (MQL). In addition, we analyze semantic conflicts using case studies and provide solutions to the semantic conflicts using MQL.