SQL Workbench/J is a free, DBMS-independent, cross-platform SQL query tool. It is written in Java and thus it should run on any operating system that provides a Java Runtime Environment.

It's main focus is on running SQL scripts (either interactively or as a batch) and export/import features. Graphical query building or more advanced DBA tasks are not the focus and are not planned

Current stable version: Build 107 (2009-12-16)
Current development build: 107.5 ( 2010-02-05)

Features:

• Display result data from SQL queries (Screenshot)
• Edit, insert and delete data directly in the result table (Screenshot)
• Powerful export command to write text files (aka "CSV"), XML, HTML or SQL (including BLOB data).
  All user tables can be exported into a directory with a single command. Export files can be compress "on-the-fly".
• Powerful text and XML file import. A set of files (including compressed files) can be imported from a directory with a single command. Foreign key constraints are detected to insert the data in the correct order
• Compare two database schemas for differences. The XML output can be transformed into the approriate SQL ALTER statements using XSLT
• Compare the data of two database and generate the necessary SQL statements to migrate one to the other.
• Reformatting (Pretty-Print) of SQL Statements (Screenshot)
• Full support for BLOB data in query results, SQL statements, export and import. Read more...
• Select rows from related tables according to their foreign key definitions (Screenshot1 Screenshot2).
  
• Search text in procedure, view and other sources using a SQL command or a GUI (Screenshot)
• Search for data across all columns in all tables using a SQL command or a GUI (Screenshot)
• Copy data directly between to database servers using a SQL command or a GUI (Screenshot)
• Macros (aka aliases) for frequently used SQL statements
• Variable substitution in SQL statements including smart prompting for values (can be combined with macros)
• Auto completion for tables and columns in SQL statements (Screenshot)
• All SQL Scripts (including Workbench specific commands) can be run in batch mode
• An interactive console mode (Screenshot)
• Display table, view and procedure definitions (Screenshot)
• Display view, procedure and trigger source code (Screenshot)
• Display foreign key constraints between tables (Screenshot)
• SQLWorkbench/J is free (License agreement)