This was a hot topic in databases 20 years ago and there have been various academic projects which implemented user defined types and operators to do this for

This was a hot topic in databases 20 years ago and there have been various academic projects which implemented user defined types and operators to do this for systems like PostgreSQL. Most of them haven't produced any useful code but a quick search turned up this more promising site: http://calypso.cs.put.poznan.pl/~sqlf_j/en/index.php http://calypso.cs.put.poznan.pl/~sqlf_j/en/index.php SQLf_j is a query system, that enables fuzzy queries to relational database managements systems (currently: MySQL and PostgreSQL). The queries are written in SQLf which is an extension to SQL. SQLf_j works as a translator, that translates fuzzy queries to standard, SQL queries, and executes them with RDBMS. There also seems to be some interesting stuff here: http://www.ecst.csuchico.edu/~juliano/Fuzzy http://www.ecst.csuchico.edu/~juliano/Fuzzy