You created a view called EMP_DEPT_VU that contains three columns from the EMPLOYEES and DEPARTMENTS tables: EMPLOYEE_ID, EMPLOYEE_NAME AND DEPARTMENT_NAME. The DEPARTMENT_ID column of the EMPLOYEES table is the foreign key to the primary key DEPARTMENT_ID column of the DEPARTMENTS table. You want to modify the view by adding a fourth column, MANAGER_ID of NUMBER data type from the EMPLOYEES tables. How can you accomplish this task?

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  1. ALTER VIEW emp_dept_vu (ADD manager_id NUMBER);

  2. MODIFY VIEW emp_dept_vu (ADD manager_id NUMBER);

  3. ALTER VIEW emp_dept_vu AS SELECT employee_id, employee_name, department_name, manager_id FROM employee e, departments d WHERE e.department_id = d.department_id;

  4. CREATE OR REPLACE VIEW emp_dept_vu AS SELECT employee_id, employee_name, department_name, manager_id FROM employees e, departments d WHERE e.department_id = d.department_id;

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Correct Option: D

AI Explanation

To modify the view by adding a fourth column, MANAGER_ID, from the EMPLOYEES table, you need to use the CREATE OR REPLACE VIEW statement.

The correct answer is:

D. CREATE OR REPLACE VIEW emp_dept_vu AS SELECT employee_id, employee_name, department_name, manager_id FROM employees e, departments d WHERE e.department_id = d.department_id;

Explanation: Option A) ALTER VIEW emp_dept_vu (ADD manager_id NUMBER); - This option is incorrect because the ALTER VIEW statement does not have an ADD clause to add columns to an existing view.

Option B) MODIFY VIEW emp_dept_vu (ADD manager_id NUMBER); - This option is incorrect because there is no MODIFY VIEW statement in SQL to modify the structure of a view.

Option C) ALTER VIEW emp_dept_vu AS SELECT employee_id, employee_name, department_name, manager_id FROM employee e, departments d WHERE e.department_id = d.department_id; - This option is incorrect because the ALTER VIEW statement does not allow you to change the SELECT statement of the view.

Option D) CREATE OR REPLACE VIEW emp_dept_vu AS SELECT employee_id, employee_name, department_name, manager_id FROM employees e, departments d WHERE e.department_id = d.department_id; - This option is correct because the CREATE OR REPLACE VIEW statement allows you to create or modify a view. In this case, it creates a view called emp_dept_vu with the specified columns and queries the EMPLOYEES and DEPARTMENTS tables to retrieve the required data.

Therefore, the correct answer is option D.

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