IBM Db2

Db2 is a family of data management products, including database servers, developed by IBM. It initially supported the relational model, but was extended to support object–relational features and non-relational structures like JSON and XML. The brand name was originally styled as DB2 until 2017, when it changed to its present form. In the early days, it was sometimes wrongly styled as DB/2 in a false derivation from the operating system OS/2.

DB2 traces its roots back to the beginning of the 1970s, when Edgar F. Codd, a researcher working for IBM, described the theory of relational databases, and in June 1970, published the model for data manipulation.

In 1974, the IBM San Jose Research Center developed a related database management system (DBMS) called System R, to implement Codd's concepts. A key development of the System R project was the Structured Query Language (SQL). To apply the relational model, Codd needed a relational-database language he named DSL/Alpha. At the time, IBM did not believe in the potential of Codd's ideas, leaving the implementation to a group of programmers not under Codd's supervision. This led to an inexact interpretation of Codd's relational model that matched only part of the prescriptions of the theory; the result was Structured English QUEry Language or SEQUEL.

IBM bought Metaphor Computer Systems to utilize their GUI interface and encapsulating SQL platform that had already been in use since the mid-80s.

In parallel with the development of SQL, IBM also developed Query by Example (QBE), the first graphical query language.

IBM's first commercial relational-database product, SQL/DS, was released for the DOS/VSE and VM/CMS operating systems in 1981. In 1976, IBM released Query by Example for the VM platform where the table-oriented front-end produced a linear-syntax language that drove transactions to its relational database. Later, the QMF feature of DB2 produced real SQL, and brought the same "QBE" look and feel to DB2. The inspiration for the mainframe version of DB2's architecture came in part from IBM IMS, a hierarchical database, and its dedicated database-manipulation language, IBM DL/I.

The name DB2 (IBM Database 2), was first given to the database management system in 1983 when IBM released DB2 on its MVS mainframe platform. IBM's endorsement of SQL in Db2 caused the industry to move to it from alternatives like Ingres's QUEL. Db2 became generally available to customers in 1985, and by 1989 revenue of about $1 billion had grown to equal IMS's.

For some years DB2, as a full-function DBMS, was exclusively available on IBM mainframes. Later, IBM brought DB2 to other platforms, including OS/2, UNIX, and MS Windows servers, and then Linux (including Linux on IBM Z) and PDAs. This process occurred through the 1990s. An implementation of DB2 is also available for z/VSE and z/VM. An earlier version of the code that would become DB2 LUW (Linux, Unix, Windows) was part of an Extended Edition component of OS/2 called Database Manager.