With Check Option

This clause is very important because it prevents changes that do not meet the view's criteria.

Example: Create a view on database pubs for table authors, that shows the name, phone number and state from all authors from California. This is very simple:

CREATE VIEW dbo.AuthorsCA
AS
SELECT au_id, au_fname, au_lname, phone, state, contract
FROM dbo.authors
WHERE state = 'ca'

This is an updatable view and a user can change any column, even the state column:

UPDATE AuthorsCA SET state='NY'

After this update there will be no authors from California. This might not be the desired behavior.

Example: Same as above but the state column cannot be changed.

CREATE VIEW dbo.AuthorsCA2
AS
SELECT au_id, au_fname, au_lname, phone, state, contract
FROM dbo.authors
WHERE state = 'ca'
With Check Option

The view is still updatable, except for the state column:

UPDATE AuthorsCA2 SET state='NY'

This will cause an error and the state will not be changed.