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1 Introduction
This document explains how SQL*Plus substitution variables
work and where they can be used. It shows the relationship between the three
types of variable (substitution, bind, and system) used in SQL*Plus.
Substitution variables can replace SQL*Plus command
options or other hard-coded text. They can be used to customize SQL*Plus
script output. Substitution variable references in a statement are pre-processed
and replaced before SQL*Plus executes the statement. Variable values can
be hard coded, prompted for, or set to script parameters. Variables can also
hold values returned from queries. Sometimes substitution variables are known
as user variables or define variables.
Bind variables store data values for SQL and PL/SQL
statements executed in the RDBMS. They can hold single values or complete
result sets.
System variables contain values directly controlling
SQL*Plus, such as the line size and page size of reports. Some system variables
affect how substitution variables are processed. System variables are sometimes
called SET variables.
This document is a complete reference but you can understand
and use substitution variables in a few minutes by reading the overview in Section
2 and looking at the examples in the last section.
Section 3 and Section
4 discuss bind and system variables respectively, and how they interact
with substitution variables.
Section 5 discusses in
detail all SQL*Plus commands that interact with substitution variables.
Section 6 gives substitution
variable limits and some finer points.
Section 7 covers substitution
variables in the iSQL*Plus web based interface.
Section 8 is a brief summary
of substitution variables.
Section 9 gives a number
examples of using substitution variables.
This document updated in March 2004 for SQL*Plus Version
10.1. However all examples in this document apply to previous versions of
SQL*Plus, except where noted.
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