Explanation:
When we want to alter the underlying data used in the definition of a view, we use the CREATE OR REPLACE VIEW statement. When a CREATE OR REPLACE VIEW statement is issued, Oracle will disregard the error that arises when it encounters the view that already exists with that name, and it will overwrite the definition for the old view with the definition for the new one.
Incorrect Answers:
1: There is no ALTER VIEW command in Oracle.
2: There is no MODIFY VIEW command in Oracle.
3: There is no ALTER VIEW command in Oracle.
4: There is no MODIFY VIEW command in Oracle.
6: You don’t need to remove the existing view to create modified view. You are able to do that with CREATE OR REPLACE command.
OCP Introduction to Oracle 9i: SQL Exam Guide, Jason Couchman, p. 310-313
Chapter 7: Creating Other Database Objects in Oracle

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