DBPad is a GUI-based SQL client for relational databases. As long as you have a JDBC driver for your DB, you can use DBPad to view or manipulate your data and metadata of your tables.
JSQL Edit is a database-independent SQL client that allows graphical manipulation for making queries to databases. JSQL Edit is written in Java and uses JDBC for connectivity and Java Swing for a graphical user interface.
ProDBA The cross platform Oracle development/administration tool written in Java. Features a powerful SQL editor and schema navigator. Can export dynamic queries to the web.
ViennaSQL is a GUI SQL client written in 100% Java. ViennaSQL can communicate with any database that has a JDBC driver. It should run anywhere Java runs.