DBeaver is a freeware database manager to manage all databases that support JDBC drivers. DBeaver can connect to various database, run queries, create ERD, and manage database.

SQL Locator is a free database search engine for SQL Server to explore database without writing queries. Download SQL Locator Free.

Free Database Browser can connect to Oracle, MySQL, MS Sql Server, ODBC, PostgreSQL, SQLite, Interbase, Firebird, and OleDB. Download Database Browser Free.