insert into sm_funtouser_tb                              
      ( user_id, group_code, field_id, authority)          
select a.user_id, c.group_code, c.field_id, c.authority  
from sm_users_tb a, sm_deggroup_tb b, sm_funcgroup_tb c  
where a.user_degree = b.user_degree                    
and b.group_code = c.group_code                         
and c.group_code =  '01'        

위의 insert문을 update문으로 변환하면 어떻게 해야져??