For Dummies SQL, 7th Edition 978-0-470-55741-9 用户手册

In This Chapter

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Organizing information

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Defining “database” in digital terms

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Deciphering DBMS

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Comparing database models

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Defining “relational database” (can you relate?)

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Considering the challenges of database design

S

QL (pronounced ess-que-ell, not see’qwl, though database geeks still 
argue about that) is a language specifically designed with databases 

in mind. SQL enables people to create databases, add new data to them, 
maintain the data in them, and retrieve selected parts of the data. Introduced 
in 1970, SQL has grown and advanced over the years to become the industry 
standard. It is governed by a formal standard maintained by the International 
Standards Organization (ISO).

Various kinds of databases exist, each adhering to a different model of how 
the data in the database is organized.

SQL was originally developed to operate on data in databases that follow the 
relational model. Recently, the international SQL standard has incorporated 
part of the object model, resulting in hybrid structures called object-relational 
databases. In this chapter, I discuss data storage, devote a section to how the 
relational model compares with other major models, and provide a look at 
the important features of relational databases.

Before I talk about SQL, however, I want to nail down what I mean by the 
term database. Its meaning has changed, just as computers have changed the 
way people record and maintain information.