If you have an existing table with existing data rows, and want to add a new column to that table, you can use the ALTER TABLE ... ADD statement to do this. Here is an example script:

SQL> connect HR/globalguideline

Connected.

SQL> CREATE TABLE emp_dept_110

2 AS SELECT * FROM employees WHERE department_id=110;

Table created.

SQL> ALTER TABLE emp_dept_110 ADD (vacation NUMBER);

Table altered.

SQL> SELECT first_name, last_name, vacation

2 FROM emp_dept_110;

FIRST_NAME   LAST_NAME    VACATION

-------------------- ------------------------- ----------

Shelley   Higgins

William   Gietz

This SQL script added a new column called "vacation" to the "emp_dept_110" table. NULL values were added to this column on all existing data rows.