The DEFINE command allows you to create a user variable (or substitution variable), and to assign it a value. DEFINE may also be used to list the value of a particular variable, or of all variables. DEFINE is discussed in Chapter 4.
DEF[INE] [variable_name
[=text
]]
where:
Is the command, which may be abbreviated to DEF. Entering DEFINE by itself causes SQL*Plus to display list of all currently defined user variables.
Is the name of the variable you want to create. Issue the command with only a variable name, and SQL*Plus will display the current contents of that variable, if it exists.
Is the text you want to assign to that variable. This may optionally be enclosed by single or double quotes, which you should use any time the value contains spaces or any other nonalphabetic character.