create trigger tri_B_u
on B
for update
as
if update(number)
begin
    declare @number int,@id int
    select @id=id,@number=number from inserted--id是B表的主键
    update t6 set num=@number,total=@number*price from A where B.bookid=A.bookid and B.id=@id
end

运行下，这个，然后你修一个number看看吧。

------解决方案--------------------
SQL code


create trigger tri_B_i
on B
for insert
as
declare @id int @number int
declare @number int,@id int
select @id=id,@number=number from inserted--id是B表的主键
update B set total=@number*price from A where B.bookid=A.bookid and B.id=@id