Edgar Codd invented the relational databases model at IBM, an extremely influential general theory of data management, the foundation of RDBMS (Relational Databases Management Systems).
His employer considered it an “intellectual curiosity” at best and feared it would undermine IBM’s existing products. Codd’s ideas however were picked up by local entrepreneurs and resulted in the formation of firms such as Oracle, Ingres, Informix and Sybase. Initially, IBM refused to implement the relational model in order to preserve revenue from IMS/DB. Codd then showed IBM customers the potential of the implementation of its model, and they in turn pressured IBM.
IBM proved slow to exploit his suggestions until commercial rivals started implementing them. Initially, IBM refused to implement the relational model at all for business reasons (to preserve revenue from its current database implementation—IMS/DB.
In 1973 IBM finally included the relational model of Codd in his plans, in System R subproject, but Codd was not involved in the project. Among the critical technologies developed for System R is the Structured Query Language (SQL), developed by Chamberlin and Ray Boyce. Boyce later worked with Codd to develop the Boyce-Codd Normal Form for efficiently designing relational database tables so information was not needlessly duplicated in different tables.