Jezzper Consulting recommends Firebird 1.5 as your Open Source RDBMS.
In year 2000 Borland opened up the Inprise enterprise database as Open Source. The database was later renamed to Firebird.
Firebird is available on many platforms: Windows, Linux, Unix ....
Connectivity:
-native Component Packages for C/C++ and Delphi
-ODBC
-JDBC (JayBird)
-PHP Driver,
-OLEDB driver
-dbExpress
-.Net data provider
-direct API calls
Licence ? It's free!
Read more about Firebird:
and about the new features in version 1.5:
Links to Firebird websites
http://www.ibphoenix.com
http://firebird.sourceforge.net
If your working in Java take a look at HSQL. It has great features:
- it's free!
- 100% Java
- A full RDBMS (Relational Database Management System), with the Object capabilities of Java
- Switchable source code to support JDK 1.1.x, JDK 1.2.x, JDK (SE) 1.3.x, JDK (SE) 1.4.x.
- Standard SQL (Structured Query Language) syntax
- Correlated subqueries, inner and outer joins are possible
- Views, Temp tables and sequences
- Text Tables (with external file data sources such as csv files)
- Primary key, unique and check constraints on single or multiple columns
- ORDER BY, GROUP BY and HAVING are supported
- COUNT, SUM, MIN, MAX, AVG, alone and in expressions
- Full support for SQL language expressions such as CASE .. WHEN .. ELSE .. , NULLIF etc.
- Transaction support
- Supports Referential Integrity (foreign keys) with full cascading options (delete, update, set null, set default)
- Java Stored Procedures and Functions can be called
- Triggers
- Database Security functions
- 95% JDBC interface support with full metadata and batch statement functionality
- All JDBC 1 data types supported, also 'Object' , Blob and Clob
- In-memory, Standalone and Client-Server operating modes
- A small WebServer and a Servlet is included
- It can be used in Applets and Applications
- Autoincrement column support
- Cached or Text tables up to 2 gigabytes
- Size of strings and binary data only limited by memory
- Indexes can be created for one or many fields
- JDBC Metadata support
- Readonly connection and database support
- An SQL script describing the database can be created
read more about here :
http://hsqldb.sourceforge.net