The second generation database system is a relational database system. 1970 Edgar F. Codd, a researcher in San Jose Research Laboratory of IBM, published a paper entitled "Relational Model of Large Database Data", put forward a relational data model, established relational database methods and relational database theories, and laid the theoretical foundation for relational database technology.
The third generation database system is a data management database system. 1990, the functional committee of advanced DBMS issued the declaration of the third generation database system, and put forward three basic characteristics that the third generation database management system should have: supporting data management, object management and knowledge management. The technology of the second generation database system must be maintained or inherited. Must be open to other systems.
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The 1970s was the era of theoretical research and prototype development of relational databases, with typical representatives being System R developed by IBM San Jose Research Laboratory and Ingres developed by Berkeley University. A large number of theoretical achievements and practical experience finally make relational database move from laboratory to society. Therefore, people called the 1970s the database age.
In 1980s, almost all newly developed systems were relational, among which many commercial relational database management systems with excellent performance appeared, such as DB2, Ingres, Oracle and Informix. With the application of these commercial database systems, database technology is more and more widely used in enterprise management, information retrieval, decision-making and other aspects, and has become the basic technology to realize and optimize information systems.