Aggiornamento dati da file esterno su tabella in database sqlserver

USE tempdb;

CREATE TABLE dbo.Students(
StudentID int NOT NULL PRIMARY KEY,
FirstName varchar(10) NOT NULL,
LastName varchar(10) NOT NULL
);

CREATE TABLE dbo.StudentsStage(
StudentID int NOT NULL PRIMARY KEY,
FirstName varchar(10) NOT NULL,
LastName varchar(10) NOT NULL
);

INSERT dbo.Students 
VALUES (1, 'Lorenzo', 'Benaglia')
     , (2, 'David', 'De Giacomi');
     
INSERT dbo.StudentsStage
VALUES (1, 'Lorenzo', 'Benaglia')
     , (3, 'Matteo', 'Raumer')
     , (4, 'Marco', 'Caruso');

INSERT dbo.Students
SELECT *
FROM dbo.StudentsStage
EXCEPT
SELECT *
FROM dbo.Students;

SELECT *
FROM dbo.Students;

/* Output:

StudentID   FirstName  LastName
----------- ---------- ----------
1           Lorenzo    Benaglia
2           David      De Giacomi
3           Matteo     Raumer
4           Marco      Caruso

(4 row(s) affected)

*/

DROP TABLE dbo.StudentsStage, dbo.Students;