insert values from one table to another table in mysql

i have two tables one is table 'a' and second is table 'b'. in table 'a' there are five feilds and a_id is assigned as primary key and in second table 'b' there are two feilds and b_id is assigned as primary key.there is one common feild name in both table as cust_name.my problem is when i ins开发者_开发百科ert value in table 'a' then table 'b' should also be filled with values in the respected column. how is it possible. plz help me.

It seems like you need a trigger that will insert into b as soon as a record in inserted in a