Database management systems used in information systems for the tourism industry and based on SQL are flexible insofar as they allow queries regarding the data stored in them. However, the SQL language, in spite of its flexibility, cannot deal with the vagueness of the queries clients present to travel agencies. Questions like ''I want an inexpensive trip to an Italian city not too far from Rome'' cannot be directly answered by the system. Rather, the agent has to make different queries about available trips and then has to summarise and adapt them to the needs of the clients. A solution that gives an answer to these requirements is found in fuzzy logic sets applied to databases.
Currently, we have implemented a fuzzy SQL server (FSQL) in information systems as a result of our previous work in the field of Information Systems (IS). This server is available for Oracle databases and allows queries in traditional relational databases, as well as in fuzzy databases, by using the FSQL language (fuzzy SQL). The FSQL language is an extension of the SQL language that allows vague or fuzzy queries to databases by using fuzzy conditions (with fuzzy comparators), fulfilment thresholds, fuzzy constants, etc.
In this work we show an application of the FSQL language to the tourism sector, in particular, to the IS database of a travel agency which includes attributes with fuzzy values. That is, the database allows the storing of fuzzy values and queries with conditions involving such values. This allows the management of all the company's products to be carried out in a more efficient way and offers clients the products that best fit their requirements. Also, the system makes it possible to obtain the degree of match for each product in relation to the set obtained in the fuzzy query.