History of SQL

In the 1970's, a hot topic in computer science was persistent data.

Codasyl Data Base Task Group proposed a database language (apparently called DBTG).

Codd conceived two relational languages: Relational Algebra and Relational Calculus. Among others, Relational Calculus introduced a few interesting operators:

• ∀ : for all
• ∃ : there exists
• π : project
• σ : select
• ρ : rename
• ⨝ : join

These concepts allowed to formulate complex queries, however, they were academic in nature and difficult to enter on a keyboard. Thus, Ray Boyce and Donald Chamberlin tried to create a language that was better suited to express Codd's ideas for users. They first developed Square and then Sequel.

Sequel had no (greek or other) symbols and was generally way more readable. Boyce and Chamberlin wrote two papers:

• SEQUEL: A Structured English Query Language
• Using a Structured English Query Language as a Data Definition Language

The first paper became widely known.

Chamberlin writes about this time

Sequel was declarative rather than procedural.

Sequel evolved further within the System R project.

In 1977, the name Sequel was changed to SQL.

In 1979, Larry Ellison and Bob Miner founded Relational Software, Inc. (RSI). This company developed the first commercially viable implementation of of Codd's model with SQL. The product was sold as Oracle V.2 and was effectively the world's first relational database.

In the early 1980, IBM also began to commercially implement SQL.

1986, the first SQL standard (ISO 9075) was available, with more to follow.