SQL:1999 was the fourth revision of the SQLdatabase query language. It introduced many new features, many of which required clarifications in the subsequent. In the meanwhile SQL:1999 is deprecated.
Summary
The ISO standard documents were published between 1999 and 2002 in several installments, the first one consisting of multiple parts. Unlike previous editions, the standard's name used a colon instead of a hyphen for consistency with the names of other ISO standards. The first installment of SQL:1999 had five parts:
SQL/Framework
SQL/Foundation
SQL/CLI : an updated definition of the extension Call Level Interface, originally published in 1995, also known as CLI-95
SQL/PSM : an updated definition of the extension Persistent Stored Modules, originally published in 1996, also known as PSM-96
SQL/Bindings
Three more parts, also considered part of SQL:1999 were published subsequently:
The SQL:1999 standard calls for a Boolean type, but many commercial SQL servers do not support it as a column type, variable type or allow it in the results set. Microsoft SQL Server is one of the fewdatabase systems that properly supports BOOLEAN values using its "BIT" data type. Every 1–8 bit fields occupies one full byte of space on disk. MySQL interprets "BOOLEAN" as a synonym for TINYINT. PostgreSQL provides a standard conforming Boolean type
Distinct user-defined types of power
Sometimes called just distinct types, these were introduced as an optional feature to allow existing atomic types to be extended with a distinctive meaning to create a new type and thereby enabling the type checking mechanism to detect some logical errors, e.g. accidentally adding an age to a salary. For example: create type age as integer FINAL; create type salary as integer FINAL;
creates two different and incompatible types. The SQL distinct types use name equivalence not structural equivalence like typedefs in C. It's still possible to perform compatible operations on of distinct types by using an explicit type CAST. Few SQL systems support these. IBM DB2 is one those supporting them. Oracle database does not currently support them, recommending instead to emulate them by a one-place structured type.
