How to save datagridview null values in the datbase and also save inserted values in the database

Run Mode screen as follows; Save(Button)
 
Date Session CK RK MK Gs VB SJ

1/1/2013 1 REO PH2 TFC
 

 
Date Base Design as follows;
 
Date Datetime
Session number
Course Text
Faculty_Code Text
 
In database i want to save the above output as follows;
 
Date session Course Faculty_Code
1/1/2013 1 REo CK
1/1/2013 1 PH2 RK
1/1/2013 1 TFC MK
1/12013 1 GS
1/12013 1 VB
1/1/2013 1 Sj
 
i saved the insert values in the database it is working. i want to save null values in the database.
 
it is a windows application using c sharp.
 
how can i do.
 
when i click the save button output i get already as follows in datagridview;
 

Date session Course Faculty_Code
1/1/2013 1 REo CK
1/1/2013 1 PH2 RK
1/1/2013 1 TFC MK
 
Then i want to null values also in the database also as follows.
 
1/12013 1 GS
1/12013 1 VB
1/1/2013 1 Sj