Datasheet

Part I SQL Basic Concepts and Principles

As of this writing, all major database vendors (Oracle, DB2, and Microsoft SQL

Server) have at least partial compliance with SQL:2003, but there is no RDBMS ven-

dor on the market who meets the new standards in full. Each of the vendors has individual fea-

tures that venture into higher levels of conformance.

SQL ANSI/ISO standards are good to know, and they may help you learn the actual

SQL implementations, but it is impossible (or almost impossible) to write a real

100-percent ANSI SQL–compliant production script. You can compare this with knowing Latin,

which can help you learn Spanish, Italian, or Portuguese, but people would hardly understand you

if you started speaking Latin on the streets of Madrid, Rome, or Lisbon. The main difference is the

general direction — Latin is an ancestor of all the aforementioned (and many more) languages,

whereas ANSI/ISO SQL standards are a goal for all proprietary SQL ﬂavors.

Summary

Databases penetrate virtually every branch of human activity, with the relational database man-

agement system (RDBMS) becoming the de facto standard. Some legacy database models —

hierarchical and network databases — are still in use, but the relational database model holds

the lion’s share of the market.

The RDBMS resolves some of the inherent problems of the legacy databases, and — with the

advent of faster hardware and support from the industry heavyweights — became the staple of

every business enterprise. The new object-oriented database systems (OODMS) are evolving,

although none has reached the level of acceptance comparable with that of RDBMS. The object-

oriented features became a part of SQL standards, and all major vendors are implementing them

to certain degree, gradually becoming object-oriented relational database systems (OORDBMS).

XML became a part of SQL standard in 2003, and is becoming more and more popular.

Oracle, Microsoft, and IBM, as well as many other smaller vendors, are adding XML features to

their RDBMS products.

Most of the existing applications on the database market use SQL as the standard language.

There have been four generations of the standard so far: SQL-86/87 and SQL-89, SQL-92,

SQL:1999, and SQL:2003 (SQL:2008 is coming) with virtually every RDBMS product being at

least partially SQL:2003-compliant.

SQL as the language of the RDBMS has been on the market for almost 30 years, and everything

indicates it will be around in the foreseeable future. SQL proved to be user-friendly and ﬂexible

enough to accommodate new features, and is constantly evolving, as are the SQL standards.