Chapter 7. Basic SQL

Back in the '70s the father of the relational database concept, E. F. Codd, invented the first version of Structured Query Language (SQL) at IBM. The model described by Codd was based on tables that could be linked with each other. These tables are called relations.

IBM spent a lot of money to implement software based on Codd's ideas, and in 1978 a product called System/R was introduced. However, other companies have implemented relational databases faster than IBM. The first company to offer a relational database was Oracle, and shortly after Oracle, Ingres was available. In 1982 IBM released improved products called SQL/DS and DB2, which is still a major player in the database arena.

The language relational databases are based on is SQL. SQL is an open standard that does not belong to a company, and this may be one reason why SQL has become so successful in the database arena. The commercial success of SQL was precipitated by the formation of the SQL Standard committees by the American National Standards Institute (ANSI) and the International Standards Organization (ISO) in 1986 and 1987. In 1989 the specification of SQL-89, also known as SQL-1, was published. In 1992 SQL-2, which is also known as SQL-92, was introduced. SQL-92 added some extensions to SQL-89 the entire standard was already some 600 pages long. The most recent version of SQL is SQL-99, which is also known as SQL-3.

Although there is a unitary SQL standard, many flavors and accents of SQL are available. Every database system provides a slightly different implementation of the standard, and so does PostgreSQL. Although the goal of PostgreSQL is to be 100% standard-compliant, there are some minor differences.

In this chapter you will be guided through SQL and you will learn to work with tables as well as other components of relational databases.