Sqlite Update a column value from another table using triggers

I have a table A with columns (..,subject,data,..) and table B with columns (..,subject,data,ref,..). Each row of table B has a foreign key reference to a row table A (lets call it ref).

When a row is inserted(or updated) into table B, only ref value will be present. I want to read the subject and data values from A and insert into B using triggers. I am new to using triggers. Can someone tell me if it is feasible?