Ingres was one of the first working relational database systems. It was built at the University of California, Berkeley by a team led by Michael Stonebraker and Eugene Wong, alongside Peter Kreps and Gerald Held. Their 1976 technical report “The Design and Implementation of Ingres” (UCB/ERL M577) describes a multiuser system that “gives a relational view of data” and runs as a collection of user processes on top of the Unix operating system for DEC PDP-11/40, 11/45, and 11/70 computers.
Where IBM’s contemporary System R introduced the SQL language, Ingres offered its own high-level nonprocedural query language, QUEL. Both projects independently demonstrated that Edgar Codd’s relational model — proposed in 1970 — could be turned into a practical, performant database management system rather than remaining a piece of theory.
Because the Berkeley code was distributed openly with source, Ingres seeded a remarkably large family of commercial systems. Descendants and offshoots of its design and its people fed into Sybase, Microsoft SQL Server, Informix, and others, and the project’s direct successor at Berkeley, Postgres, became the basis of modern PostgreSQL.