摘要： 在模糊理论的基础上，将权重概念引入关系数据库模糊查询中，以体现用户对查询中各个属性的相对重视程度。记录按匹配度的降序输出，方便用户选择。权重和匹配度都是语言变量，取值为语言值，更加贴近自然。采用模糊集合的alpha截集去模糊的思想，将带语言值权重的模糊查询条件转化为精确的SQL语句，利用RDBMS的机制进行记录的筛选，避免对整个数据库表的扫描，在一定程度上保证查询的效率。

关键词: 模糊查询, 语言变量, 权重

Abstract: The concept of weight is introduced in fuzzy queries based on theory of fuzzy set, which shows the relative importance that users pay to different attributes in query clauses. The records that satisfy queries are output according to the decrease of matching degrees, so users can select what they want more conveniently. Weights and matching degrees are linguistic variables, whose values are linguistic terms, and the queries become more flexible. The alpha-cut of fuzzy set is used to translate the linguistic fuzzy querying conditions into crisp SQL clauses. It is possible to make use of the mechanism of RDBMS to filter the records, which avoids scanning the whole table and assures the efficiency.

Key words: fuzzy queries, linguistic variables, weight

中图分类号: 

• TP311