Re: what is the difference between th DBMS and RDBMS?

Historically, there have been various types of DBMS

The hierarchical database, maintaing physical pointers between various entities, n:m relations not implemented. The Network database, same type of database, n:m allowed. The most important implementation was IBM's IMS (acronym for IBMs Most Spectacular).
The Relational database, implementing entities as tables.

IBM, iirc, still supports IMS, as major insurance companies and banks all over the world are still using it. RDBMS has supplanted network databases.

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Sybrand Bakker
Senior Oracle DBA