SQuirreL SQL Client is a graphical SQL client written in Java, which allows you to view the structure of a JDBC compliant database, browse the data in tables, and, amongst other things, issue SQL commands. The graphical front end is built to support JDBC-compliant databases, and the great thing about using SQuirreL SQL Client is that the functionality can be extended with the use of plugins!
SQuirreL SQL Client lets you install and create plugins, which are designed to augment the functions of the core application. There are a number of plugins available for download on the SQuirreL SQL Client website.
SQuirrel SQL Client is a really handy tool for database administrators who need to analyze the structure of JDBC compliant databases by configuring the proper drives and aliases such as FrontBase, MySQL, Oracle, PostgreSQL, Oracle, InstantDB.
Overall, SQuirreL SQL Client is easy to install and use. It has been successfully tested with a number of databases, including IBM DB2. It is relatively fast and not too large or resource hungry. There is plenty of support for the client via mailing lists etc, on the SQuirrel Client home page.