|
|
What is a Relational Database Management System (RDBMS)?
A set of software that enables the user to create, review, update and delete information held in a relational database.
What are some popular RDBMSs which support SQL?
What is the history of RDBMSs?
Dr E.F.Codd of IBM published "A Relational Model of Data for Large Shared Data Banks ", in the Communications of the ACM in 1970. This is the mathematically rigorous theoretical base of the relational databases. Subsequently, he published his famous 12 principles of relational databases in "The Relational Approach to Data Base Management: An Overview", at the Third Annual Texas Conference on Computing Systems in 1974.
What are the different kinds of database management systems?
While hierarchical and network databases are older than relational databases, object and object - relational databases are of relatively recent origin.
What are the features of a hierarchical database?
The main structures used by the hierarchical model are record types and parent-child relationship between a parent record type and a child record type. Access to lower level data elements must first access their parents. Relationships are strictly hierarchical in that a record type can participate as child in at most one parent-child relationship type. This restriction makes it difficult to represent a database where numerous relationships exist. While storage and retrieval are very fast, it is difficult to query a hierarchical database, and impossible to build decision support systems based on it.
What are the features of a network database?
The network model assumes a more complex interrelationship (many to many) between data elements. Relationships and access paths are still predetermined and usually fixed but less restrictive. A record type can participate as owner or member in any number of set
