Database Reference
In-Depth Information
add an additional, unique numerical attribute called
id
as our primary key, as we can't
guarantee that there are not two distinct Edgar Codds. Finally, we can use an SQL
query that returns a relationship between the names of the computer scientists and
which country they are from.
Listing 3.1
A simple relational database model and SQL query
Table #1: countries
Name abbreviation
--------------------------------------------------------
United Kingdom UK
United States USA
Table #2: people
Id first last nationality
--------------------------------------------------------
1 Edgar Codd United Kingdom
2 Alan Turing United Kingdom
3 Eric Brewer United States
/* Example SQL Query */
SELECT
people.id, people.first, people.last, countries.abbreviation
FROM
people, nationality
WHERE
countries.name = “United Kingdom”;
# Result
1, Edgar, Codd, UK
2, Alan, Turing, UK
Relational databases allow for a very f lexible model for storing and querying data.
Putting work into the design of the schema of data provides great benefits, such as the
ability to express a variety of queries. The relational database model provides an acces-
sible interface to complex data problems and a method for unlocking the value of data.
Codd published his ideas about the relational database model in 1970. At first,
Codd's employer, IBM, took its time commercializing this technology. It took nearly
a decade for IBM to develop a product based on Codd's theories for database design.
While Big Blue was taking its time bringing the relational database to market, many
others were recognizing the value of Codd's relational concept. Among these was
none other than Larry Ellison, who helped found a company with the inauspicious
name Software Development Laboratories. This company later evolved into Oracle,
and Ellison's commercial success made him one of the richest people in the world. The
relational database market sparked intense competition throughout the 1990s, with
behemoths including Sybase and Microsoft joining Oracle and IBM in the scrum for
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