SQL Bible [Electronic resources] نسخه متنی

Summary

SQL built-in functions complement
inherent deficiencies in the nonprocedural language. They perform many tasks,
ranging from rounding numbers to strings manipulation to conversion of data
types into the sophisticated logic of substitute functions like
DECODE.

While the number of functions defined in
SQL92/99 standards is relatively small, every RDBMS vendor has its own set of
these useful tools well in excess of hundreds. Therefore, it should not come as
a surprise that functions differ across the vendors — in capability,
implementation details, syntax, or simply being included or excluded from the
implementation.

This chapter contains a comprehensive
overview of the most important functions, as well as the correspondence between
the three RDBMS implementations in terms of producing similar outcomes. The
function classifications in this chapter are based on the data types of the
arguments used by the functions to perform operations (for example, character
data, numeric data, date), and on general functionalities (like conversion).
Some functions that have advanced or nonstandard features are included in the
chapters that discuss topics relevant to those functions: security functions
are covered in the security chapter, and XML functions are part of the chapter
on latest SQL developments.