Update and Insert data from a updated table
Requirements are not clear on insert. 
If the ID are not correct then how would you know a non-matching usercode is not already present?  

Update:
What this does is if t2 is null then it will not replace a value in t1

update t1 
set t1.col1 = insull(t2.col1, t1.col2) .... 
from table1 t1 
join table2 t2 
on t2.usercode = t1.usercode