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SQL in a Nutshell by Kevin Kline

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Chapter 5. Unimplemented SQL99 Commands

The SQL92 and SQL99 standards specify many commands. However, RMBDS vendors are not able to implement all of them immediately. In fact, many commands specified in the new SQL99 standard are nowhere near being implemented by any of the database vendors covered in SQL in a Nutshell. In effect, these commands exist because the standard says they exist, but they cannot currently be executed anywhere. As a result, these commands are described only briefly in Table 5.1.

Nonetheless, it should be noted that although these commands are not implemented yet, they could be eventually. Consequently, it is important to check vendor documentation to see if the newest version has implemented any of these commands.

Table 5-1. Unimplemented SQL99 Commands

Commands

Description

ALLOCATE CURSOR

The ALLOCATE CURSOR statement is used in Dynamic SQL to link a SELECT statement initialized with the PREPARE statement. This statement differs from DECLARE CURSOR in that ALLOCATE CURSOR creates multiple precompiled cursor statements while DECLARE CURSOR is created and compiled dynamically each time it is run.

ALLOCATE DESCRIPTOR

This statement prepares a dynamic area that stores information about the parameters in a dynamically generated SQL statement. In effect, this command allows the amount of space set aside for dynamic SQL statements to be controlled precisely.

ALTER DOMAIN

A domain is generally a user-defined datatype. According to the SQL99 standard, ...

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