The Word Of Codd
Without the pioneering work of Edgar F Codd, a British computer scientist, the world may never have known of Relational Databases.
Folks starting out with Relational Databases often get confused. I always get confused when I start something new so I know how you feel. Here is a simple explanation from Edgar Codd -who invented Relational Databases, The Wheel, Electricity and Hamburgers back in 1969. He actually only invented one of these things - can you guess which?
Its core idea is to describe a database as a collection of predicates over a finite set of predicate variables, describing constraints on the possible values and combinations of values. The content of the database at any given time is a finite (logical) model of the database, i.e. a set of relations, one per predicate variable, such that all predicates are satisfied. A request for information from the database (a database query) is also a predicate.
Got that? No, I don't understand a word of it either!
Mr Codd gave us his twelve rules ( I'm sure you will spot the hilarious joke as there are, in fact thirteen rules, the first one is numbered zero! Oh how us sad techie types laughed...). Although Mr Codd's rules are not very useful to us in Simon Larkin's Techniques and Tips for Effective and Usable Real World Database Design Methodology or SLTTEURDDM for short - one of the pages in this tutorial details all of Codd's rules.
The IBM Conspiracy
I have no idea why I said 'Conspiracy', just IBM sounded a bit terse for a heading.
Three folks must be remembered - Edgar F Codd, Chris Date and Raymond F Boyce. These IBM computer scientists did some of the earliest work on relational database methodology and normalisation - more later. There is a really good Wikipedia page on Edgar F Codd that offers a fascinating (to us database geeks anyway) insight into the development of database technology.
SQL was developed at IBM by . Chamberlin and Raymond Boyce in the early 1970s. It was originally called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM's first crack at a relational database management system.
I remember the days before Relational Databases, we used these quaint things called Files. Well, we still use files , it;s just that the RDBMS ( Relational Database Management Systems) hide them from us! The next page in this tutorial shows how Flat files used to work - well I suppose databases are still files, but all the hard work is done by the RDBMS these days.