How to add to a database table without repeats?

Question

SQL Server

I have a table. I fill it with students. Then I delete some rows from the table. How can I add only those lines that have been removed? If you fill in the primary key again, then there will be an error that such ones already exist. And if you turn it off, then there will be duplicates.

Answer 1

insert into Students
select list.Id, list.[Name] 
from 
(values	
  (1,N'Вася'),
  (2,N'Петя'),
  (3,N'Женя'),
  (4,N'Коля'),
  (5,N'Настя'),
  (6,N'Аристарх'),
  (7,N'Никодим')
) list (Id, [Name])
left join Students s on s.Id = list.Id
where s.Id IS NULL

Answer 2

Maybe INSERT ON DUPLICATE KEY UPDATE will do?