Recently, Oracle, IBM, and Microsoft are famous for Relational Database. those three companies mostly keep 90% of the market share of database. However, question came up.
Which company did develop it and start servicing it?
Edger F. Codd who worked at IBM wrote a essay titled "Derivability, Redundancy, and Consistency of Relational Store in Large Data Banks" in 1969. Database is based on contents of that essay. It talks about definition of relational algebra and calculus, and using predicate logic for controlling database. this is the origin of Relational Database.
in 1973, IBM launched project "System R." at the same time, Michael Stonebraker who was in University of California, Berkeley launched original project INGRES(Interactive Graphics Retrieval System), inspired by essay of project System R.
INGRES by Stonebraker had developed gradually and it had supported to create other RDBMS such as Sybase, SQL server, Informix, and so on.
Larry Ellison who was in Ampex cooperated with his bosses to establish a company Software Development Laboratories in 1977. it had changed name of company to "Relational Software Inc." in 1979 and it had changed its name again to "Oracle Corp." in 1983. They made the world's first relational database management system(RDBMS) on UNIX in 1979. IBM made RDBMS which ran only on VSE in 1981 and another type of RDBNS which ran on only MVS in 1983. As diffusion of UNIX in 1980s, Oracle's RDBMS became popular because its RDBMS is based on C which is highly portable language. on the other hand, IBM's RDBMS could run on only IBM's OP.