Bind variables can even be referenced by SQL queries : Variable « SQL PLUS Session Environment « Oracle PL/SQL Tutorial

SQL>
SQL> SET ECHO ON
SQL> 
SQL> VARIABLE  s_table_name  varchar2(30)
SQL>
SQL> 
SQL> BEGIN
  2    :s_table_name := 'emp';
  3  END;
  4  /

PL/SQL procedure successfully completed.

SQL>
SQL> 
SQL> SELECT index_name
  2    FROM user_indexes
  3   WHERE table_name = :s_table_name;

no rows selected

SQL>
SQL> SET SERVEROUTPUT ON
SQL> BEGIN
  2    DBMS_OUTPUT.PUT_LINE(:s_table_name);
  3  END;
  4  /
emp

PL/SQL procedure successfully completed.

SQL>

29.61.Variable
	29.61.1.	Use 'variable command' to define variable to reference cursor
	29.61.2.	Bind variables can be declared in your SQL*Plus script,Preface a bind variable with a colon to reference it in a PL/SQL block
	29.61.3.	Bind variables can even be referenced by SQL queries
	29.61.4.	Define variable and print its value out
	29.61.5.	Define variable and set value
	29.61.6.	Define variable and use it in sql statement
	29.61.7.	Print variable out
	29.61.8.	Undefine variable
	29.61.9.	Check pre-defined variables
	29.61.10.	Use defined-variable in update set statement