create table t1
(
c1 number,
c2 number,
c3 number,
constraint t1_pk primary key (c1)
)
;
create table t2
(
c1 number,
c2 number,
c3 number,
constraint t2_pk primary key (c1)
)
;

merge into t2
using (select * from t1)
on (t1.c1=t2.c1)
when matched then
 update set t2.c2= t1.c2 where t2.c2 != t1.c2
 update set t2.c3= t1.c2 where t2.c3 != t1.c3
when not matched then
 insert  (t2.c1,t2.c2,t2c3) values (t1.c1,t1.c2,t1.c3)
;

 update set t2.c2= decode(t2.c2,t1.c2,t2.c2,t1.c2), t2.c3= decode(t2.c3,t1.c3,t2.c3,t1.c2) where t2.c2 != t1.c2 or t2.c3 != t1.c3

update set t2.c2=case when t2.c2=t1.c2 when t2.c2 else t1.c2 end