Question

I know the column for doing the reverse process (nullable to nonnullable) is

ALTER TABLE [Course_Enrollment] ALTER COLUMN [enrollment_date] DATETIME NOT NULL

But what about going from nonnullable to nullable? (I don’t want to mess things up, by removing the NOT from the above SQL and therefore I might risk changing the default value to NULL.)

Answer 1

This is correct as you assumed:

ALTER TABLE [Course_Enrollment] ALTER COLUMN [enrollment_date] DATETIME NULL;

In a nullable column the default is in fact NULL unless you specify otherwise.