Oracle Database Interview Question:

How To Add a New Column to an Existing Table with a Default Value?

Submitted by: Administrator

If you want to add a new column to an existing table, and insert a default value in this column on all existing data rows, you can use the ALTER TABLE ... ADD statement with the DEFAULT clause. Here is an example script:

SQL> CREATE TABLE emp_dept_90
2 AS SELECT * FROM employees WHERE department_id=90;
Table created.

SQL> ALTER TABLE emp_dept_90
2 ADD (vacation NUMBER DEFAULT 10);
Table altered.

SQL> SELECT first_name, last_name, vacation
2 FROM emp_dept_90;
<pre>FIRST_NAME LAST_NAME VACATION
-------------------- ------------------------- ----------
Steven King 10
Neena Kochhar 10
Lex De Haan 10</pre>
As you can see, the "DEFAULT 10" clause did inserted 10 to all existing data rows.
Submitted by: Administrator