A tool that parses SQL Select statements and generates a diagram. The diagram shows parts of the underlying SQL directly in the diagram. For example x=30 , GROUP BY (year), HAVING MIN(age) > 18. It is easy to see cartesian joins and/or loops.
Reverse snowflake Joins (or reverse engineer SQL query or graphical SQL viewer) is very usefull for DBA and others dealing with complex queries analysis. Try it at http://snowflakejoins.com/ (demo site) there is no need of the database as it works directly with the SQL statement. Regards PAscal