How to update fields in the target table in correspondance with the source file values

Question

Environment: win7, SQL server 2008 R2
Application: Microsoft Management SQL Studio 2008 R2, Business Intelligence 2008 - SSIS
SSIS competency level: Novice
Problem: I have been trying to update some of the fields in the destination table,student table, in reference to data set in the staging table and ssn table.  I was able to insert/load new data to the destination using look up transformation
while the driver is ssn (data mapping) but i couldn't know how to update some of the fields in the student table while keeping the orignal pn_id of both tables(ssn and student tables), because pn_id already exists in the SSN table and student table. There
are other records also associated with the pn_id so I am not allowed to update the pn_id in the destination tables. For example,
SSN Table (pn_id,ssn)
('000616850',288258466)
('002160790',176268917)
Staging Table (ssn, id, pn_id, name, subject, academic year, comments)
(288258466, 1001, '770616858',Sally Johnson, English,A, 2005,'great student')
(176268917, 1002, '192160792',Will Smith, Math,38000,C, 2014,'no comments')
(444718562, 1003, '260518681',Mike Lira, Math,38000,B, 2013,'no comments')
Student Table (destination table)(id,pn_id,subject,academic year, grade, comments):
(1001, '000616850', ' ',' ', ,'')
(1002, '002160790', ' ',' ', ,'')
Expected Results:
My goal is to have student table updated as the following:
Student Table
(1001, '000616850', 'English','A' ,2005 ,'great student')
(1002, '002160790', 'Math ',' C',2014 ,'no comments')
please advise

Answer 1

Why can't you use simple UPDATE command in EXECUTE SQL Task as below,
DROP TABLE SSN
DROP TABLE STAGING
DROP TABLE STUDENT
CREATE TABLE SSN(pn_id VARCHAR(100),ssn BIGINT)
INSERT INTO SSN VALUES('000616850',288258466)
INSERT INTO SSN VALUES('002160790',176268917)
CREATE TABLE Staging (ssn BIGINT, id INT, pn_id BIGINT, name VARCHAR(100), subject VARCHAR(100),grade VARCHAR(10), [academic year] INT, comments VARCHAR(100))
INSERT INTO Staging VALUES(288258466, 1001, '770616858','Sally Johnson', 'English','A', 2005,'great student')
INSERT INTO Staging VALUES(176268917, 1002, '192160792','Will Smith', 'Math','C', 2014,'no comments')
INSERT INTO Staging VALUES(444718562, 1003, '260518681','Mike Lira', 'Math','B', 2013,'no comments')
CREATE TABLE Student(id INT,pn_id BIGINT,subject VARCHAR(100), [academic year] INT, grade VARCHAR(10), comments VARCHAR(100) )
INSERT INTO Student VALUES(1001, '000616850', NULL,NULL,NULL ,NULL)
INSERT INTO Student VALUES(1002, '002160790', NULL,NULL,NULL ,NULL)
UPDATE Student SET Subject = C.Subject, [academic year]=C.[academic year], grade=C.grade,comments=C.comments
FROM SSN A INNER JOIN Student B
ON A.pn_id=B.pn_id INNER JOIN Staging C
ON A.ssn = C.ssn
SELECT * FROM Student
Regards, RSingh