Oracle variables are a great way of removing duplicate SQL statements from your Oracle SQL scripts. By using a variable, you can store the return value of a query and use it later in another, as this example illustrates:

COLUMN your_column new_value your_variable;

SELECT DISTINCT (your_column)
                                 FROM ...
                                WHERE ...;

SELECT &your_variable FROM dual;

The above example stores the value of the SELECT DISTINCT query in a variable named your_variable. You declare the variable with new_value, and set the value by executing an SQL statement that returns one row and column.