Dialects of SQL
The constantly evolving nature of the SQL standard has given rise to
a number of
SQL
dialects among the various vendors and products.
These dialects most commonly evolved because the user community of a
given database vendor required capabilities in the database before
the ANSI committee created a standard. Occasionally though, a new
feature is introduced by the academic or research communities due to
competitive pressures from competing technologies. For example, many
database vendors are augmenting their current programmatic offerings
with Java (as is the case with Oracle and Sybase) or VBScript (as
Microsoft is doing). In the future, programmers and developers will
use these programming languages in concert with SQL to build SQL
programs.
Nonetheless, each of these dialects includes conditional processing
(such as that controlled through IF . . . THEN
statements), control-of-flow functions (such as
WHILE loops), variables, and error handling.
Because ANSI had not yet developed a standard for these important
features, RDBMS developers and vendors were free to create their own
commands and syntax. In fact, some of the earliest vendors from the
1980s have variances in the most elementary commands, such as
SELECT, because their implementations predate
the standards. (ANSI is now refining standards that address these
shortcomings.)
Some of these dialects have introduced procedural commands to support the functionality of a much more complete programming language. For ...