Change uniqueidentifier

-- alter table University add GID uniqueidentifier not null DEFAULT (newsequentialid())

--ALTER TABLE Student ALTER COLUMN UniversityID nvarchar(250) -- [null | not null]
--alter table Student drop CONSTRAINT FK_Student_University

begin tran
begin try

DECLARE @ID NVARCHAR(250)='';
DECLARE @G_ID NVARCHAR(250)='';

DECLARE Table_Cursor CURSOR
FOR

SELECT ID,GID from University

OPEN Table_Cursor FETCH NEXT FROM Table_Cursor INTO @ID,@G_ID
WHILE (@@FETCH_STATUS = 0)
BEGIN

update Student set UniversityID=@G_ID where UniversityID=@ID

FETCH NEXT FROM Table_Cursor INTO @ID,@G_ID
END CLOSE Table_Cursor DEALLOCATE Table_Cursor

COMMIT
END TRY
BEGIN CATCH
ROLLBACK
END CATCH