drawDB - Free, simple, and intuitive online database design tool and SQL generator.
DBeaver - DBeaver - Universal Database Manager and SQL Client.
Hive - Seamless project management and collaboration for your team.
HeidiSQL - HeidiSQL is a powerful and easy client for MySQL, MariaDB, Microsoft SQL Server and PostgreSQL. Open source and entirely free to use.
dbForge Studio for PostgreSQL - dbForge Studio for PostgreSQL is a universal GUI tool for PostgreSQL databases development and management with options to create and execute queries in the IDE.
HSQLDB - hsqldb: Full-featured 100% Java ORDBMS