How to Alter the foreign key in MS SQL

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SQL-Server-2005

SQL

SQL-Server

Hello ,
I have a problem.I need to alter a foreign key in a table which I have created in MS SQL express 2008.

Here is the sql code for the table I have created.

CREATE TABLE marks
(
id idType identity not null primary key,
studentID int not null FOREIGN KEY REFERENCES student(id) ON UPDATE CASCADE,
marks int CHECK(marks >=0 and marks <= 100)
)

What i Need to do is Alter foreign key as follows

1.I need to drop studentID
2.I need change referential integrity of the column (which has foreign key)
Eg ON DELETE NO ACTION

Here is the code I tried

ALTER TABLE marks
ALTER COLUMN studentID ON DELETE NO ACTION
AlTER TABLE marks
DROP FOREIGN KEY studentID

Thank you