This document is a brief collections of information available through old published books and internet; I did not have chance to check all cross references to validate  the time lines.

As a personal bias I was more curious about PostgreSQL database; I learned Oracle database first then others. Therefore, I reviewed Oracle's organizational history than structural nut-bolts.

Here I document my inclinations towards these databases only, than be a critique of any system or application.   

1970s-Assembly Language , SDL To RSI

Larry Ellison with Bob Miner and Ed Oates of Software Development Laboratories (SDL) started Relational Software Inc, where Oracle precursor was written in assembly language. Oracle version 1 was not released officially, Oracle version 2 was released around 1979

1980s  RSI to Oracle Systems Corporation

Oracle version 3 was developed with C programming language, and to run in mainframe and mini computers. It supported the execution of SQL statements and transactions. The version 5 was the land mark of introducing clustering , and in 1986 SQL*Plus was available to the users. The PL/SQL surfaced with the version 6.

1990s and 2000s: Oracle releases

Oracle 7, Oracle 8, 8i, 9i were release. As a landmark Oracle 7 revisions,  supported dynamic SQL Video, the version 8 started supporting Java, HTML and network computing, the version 9i RAC surfaced.

The object Model of Oracle 8i, supported the user defined ( table and column) data type, in this system OID  (Identifying Each Object) was integrated. However did not support any inheritance (it was then , for now please refer this linkType Inhertance

Oracle release 10g was released supporting Linux 64bit, (g stands for grid computing) in which resource of each computer in a network could be accessible through one lead computer often addressed as "Node".

Data Block : Oracle manages the storage space in the datafiles of a database in units called data
blocks. A data block is the smallest unit of data used by a database. Oracle stores datafiles in data block (logical block or pages), requests multiple datablock of it's own, not the ones managed by operating systems. A specific number of blocks constitutes an extent, set of extents constitute a segment.

1970s-Ingres-RDBMS

PostgreSQL as a database has a long history. In the late 1970s, the University of California at Berkeley started  a created of a relational database known as Ingres. Relational Technologies commercialized this DB as Ingres. Relational Technologies became Ingres Corporation, and was later acquired by Computer Associates.

1980s-Ingres To Postgres
 A team led by Michael Stonebraker from UC Berkeley led, added object-oriented features to Ingres and named as Postgres. Postgres was then commercialized; by Illustra, which became a part of the Informix Corporation.

1990s-Postgres To PostgreSQL

Postgres used a specific query language known as Postquel, which was based on QUEL. Andrew Yu and Jolly Chen added SQL support to the existing  Postgres database in the mid-'90s.  In 1996, many new features were added, including the MVCC transaction model, more adherence to the SQL92 standard, and many performance improvements. Postgres once again acquired a new name, PostgreSQL.

The older versions of PostgreSQL, you could run the PostgreSQL server on a Windows host but you had to install a Unix-like infrastructure (Cygwin) first: PostgreSQL wasn't a native Windows application. Starting with PostgreSQL version 8.0, the
PostgreSQL server has been ported to the Windows environment as a native-Windows application.

Before PostgreSQL 8.0, PostgreSQL server was required to have Unix-like infrastructure (Cygwin) in windows. The version 8.0 and onwards, PostgreSQL can be installed in windows environment.

• http://www.dba-oracle.com/t_history_oracle.htm
• http://www-css.fnal.gov/dsg/external/freeware/mysql-vs-pgsql.html