Thanks guys, I was able to resolve it. Here is my query:

I created a dummy table
create table test_dummy
as (select b.point_value
from table_assn b,
where b.id = a.id
and b.point_value != a.point_value)

then

update table_tmp
set point_value = ( select point_value from table_assn where table_assn.id = table_tmp.id )
where EXISTS ( select point_value from table_assn where table_assn.id = table_tmp.id)