Format:

column column_name new_value var_name

Meaning:

use the column_name of a select statment to construct a variable, later we can use &var_name to refer its value.

If the Select statement returned more that one row, the last row value will be assigned  to the variable.

 Example 1:

-- create directory and varchar2 arraycol value new_value user_dump_directory;select value from v$parameter where name = 'user_dump_dest';create or replace directory user_dump_dir as '&user_dump_directory';

Example 2

create table new_value_test_from (  some_field_name Varchar2(20));create table new_value_test_to (  another_field Varchar2(20)); insert into new_value_test_from values ('Maegerli Mucki');column some_field_name new_value some_var_nameselect some_field_name from new_value_test_from;insert into new_value_test_to values ('&some_var_name');select * from new_value_test_to;drop table new_value_test_from;drop table new_value_test_to;

create table new_value_test (  some_field_name Varchar2(20));Example 3 insert into new_value_test values ('Maegerli Mucki');insert into new_value_test values ('Globi');column some_field_name new_value some_var_nameselect some_field_name from new_value_test;drop table new_value_test;