HTSQL a high-level query language and Web service gateway for relational databases. It comes with source code and is royalty free for any use with open source database systems such as MySQL, PostgreSQL, SQLite, etc. Licenses for using HTSQL in conjunction with proprietary databases such as Microsoft SQL and Oracle can be purchased.
DBeaver is a universal database manager and SQL Client. It supports MySQL, PostgreSQL, Oracle, DB2, MSSQL, Sybase, Mimer, HSQLDB, SQLite, Derby, and any database that has a JDBC driver. It is a GUI program that allows you to view the structure of a database, execute SQL queries and scripts, browse and export table data, handle BLOB/CLOB values, modify database meta objects, etc. It has a native UI (provided by the Eclipse SWT library), great performance, and relatively low memory consumption.