Relational Database (RDB) is arguably the most widely used repository for database applications. Since the 1970s, we have witnessed the relational data model, from which the RDB is originated, evolving. The progress aims to answer the increasing requirement in database applications. One of them is the requirement to deal with complex structure of real world problems. Unlike its Object-Oriented Database (OODB) counterpart, the RDB, for example, does not have facilities to store large structured objects, semi-structured data, and so forth.