create table a_bba_tst
as 
select 1 id, 0 col1 from dual
union all 
select 2 id, 0 col1 from dual
union all 
select 3 id, 0 col1 from dual
union all 
select 4 id, 0 col1 from dual;
---
create table b_bba_tst
as 
select 1 id, 1 del_flg from dual
union all 
select 2 id, 1 del_flg from dual
union all 
select 3 id, 1 del_flg from dual
union all 
select 4 id, 1 del_flg from dual;
--------------
merge into a_bba_tst a
using 
  (select *
     from b_bba_tst) u
 on (u.id = a.id)
when matched then 
  update set a.col1 = u.id 
     where u.del_flg = 0
  delete 
     where u.del_flg = 1;
     
select * from a_bba_tst;
ID	COL1
1	0
2	0
3	0
4	0