sql - Join when exact match other other wise join with default value -

i have 2 table , b

table a

   id          b     c

table b

   id           value                1       b             2    default       0

so want join 2 tables on id when matching, otherwise use default value desired results

   id           value                1       b             2    c             0

use left outer join purpose like

select t1.id, coalesce(t2.value, 0) value tablea t1  left join tableb t2 on t1.id = t2.id;

Erty