Chapter 4: Introducing Transact-SQL Language


Overview

In the early days of relational databases, a number of industry-wide efforts were made to unify different, proprietary query languages. IBM had established an early standard called Structured English Query Language. This name was condensed to literally spell the word SEQUEL. Another effort resulted in a language called Select Query Language (SQL) that included commands allowing data to be read only for reporting and record look-up. This became a popular, product-independent standard to which the "Sequel" acronym was still applied by members of the database community. Eventually, additional commands were added, enabling records to be added, deleted, and modified. This created a quandary. They had worked so hard to create a standard language with a cute name that no longer fit. The word Select was finally replaced with the word Structured. . . and the universe was once again brought back to a state of balance. Of course, the purists will insist that SQL is pronounced ESS CUE EHL, rather than "SEQUEL." So, how should you pronounce it? Any way you want. Disagree if you like, but I save one syllable and say "SEQUEL."

For the SQL language to survive outside of a specific product or company, the standard was published and held by an independent standards organization. The SQL standard was originally registered with the American National Standards Institute and officially called the ANSI SQL standard, established in 1986. This standard has been revised a few times, resulting in revisions known as the following:

  • ANSI SQL-86

  • ANSI SQL-89

  • ANSI SQL-92

  • ANSI SQL-99

  • ANSI SQL-2003

The concept seems quite simple but there is a little more to this story. The ANSI SQL standard is actually no longer held exclusively by the American National Standards Institute. This is a common tale of American-born standards that are later implemented internationally. In 1987, SQL became an international standard and was registered with the International Standards

Organization using its previously copyrighted title, ANSI SQL. This means that the 1992 revision of the SQL standard is actually known as ISO ANSI SQL-92. Even though the standard was updated in 1999 and 2003, most SQL-based database products had been established on the ANSI SQL-92 standard and they have not been revised to fully conform to the ANSI SQL-99 or 2003 specifications. Like most of its competition, Transact-SQL does not fully conform to the ANSI SQL-99 or ANSI SQL-2003 standards but does implement selected features.

Finally, the ANSI SQL standard actually defines three conformance levels: Entry, Intermediate, and Full. Most products, including SQL Server, conform entirely to the entry-level standard and partially to the higher levels.




Beginning Transact-SQL with SQL Server 2000 and 2005
Beginning Transact-SQL With SQL Server 2000 and 2005
ISBN: 076457955X
EAN: 2147483647
Year: 2006
Pages: 131
Authors: Paul Turley

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