FUZZY QUERYING IN TRADITIONAL DATABASE

摘要

Databases are a very important component in computer systems. Because of their increasing number and volume, good and accurate accessibility to a database becomes even more important. When users work with usual software tools they have to change their many valued logical thinking (approximate reasoning) into the two-valued computer logic. Although the Structured Query Language (SQL) is a very powerful tool, it is unable to satisfy needs for data selection based on linguistic expressions and degrees of truth. The goal of the research whose results are presented in the paper is to capture these expressions and make them suitable for queries. For this purpose the fuzzy generalized logical condition for the WHERE part of SQL is developed. In this way, queries based on linguistic expressions are supported and are accessing relational databases in the same way as with the SQL. Fuzzy query is not only a querying tool; it improves the meaning of a query and extracts additional valuable information. In this paper, we are interested in flexible querying that is based on fuzzy set theory. To model the flexible queries and the concept of fuzzy attributes, an extension of the SQL language named fuzzy SQL has been defined. This architecture is based on the concept of weak coupling with the DBMS SQL Server.