求一oracle触发器语句
表A(
id number primary key,
hitnum number, --使用次数
type char(10)--类型
)
表B(
id munber,--标识
type char(10),类型
num nmber,--总使用次数，为A表中同一类型的使用次数总和
totalNum number,--为A表中同一类型的记录数量
)

在oracle中怎样建立触发器可以使往A表中增删改数据都让B中的记录与A同步,并且每次更新使系统开销尽可能小(A表中可能有同万条记录)。

根据实际情况，B不能用创建视图的方案代替，在这只能用触发器了，请教各位！

------解决方案--------------------
drop table A;
create table A(
id number primary key,
hitnum number,
type char(10)
);

create sequence seq_A start with 1;

create table B(
id number,
type char(10),
num number,
totalnum number
);

create or replace trigger trig_A 
after delete or insert or update on A
for each row
declare
v_count integer;
begin
if deleting then
begin
update B set B.num = B.num - :old.hitnum, b.totalnum = b.totalnum -1
where b.type = :old.type;

delete from b where b.num = 0 and b.totalnum = 0;
end;
elsif inserting then
begin
select count(*) into v_count from b where type = :new.type;
if v_count = 0 then
insert into b(type,num,totalnum) values(:new.type,:new.hitnum,1);
elsif v_count = 1 then
update B set B.num = B.num + :new.hitnum, b.totalnum = b.totalnum + 1
where b.type = :new.type;
end if;
end;
elsif updating then
begin
update B set B.num = B.num + :new.hitnum - :old.hitnum
where b.type = :new.type;
end;
end if;
end;
------解决方案--------------------
对你的表B的结构不是很清楚，没有主键？每次表A有操作了，都是insert into 表B?还是会更新？更新的话，假如id是主键，那岂不是永远都是1？

假设前提:
都是更新表B.不是INSERT ONLY的那种。（等于说表B里面id是起到主键的作用）

CREATE TRIGGER 表A_TRIG
AFTER INSERT OR UPDATE OR DELETE
ON 表A
FOR EACH ROW
BEGIN
IF INSERTING THEN
INSERT INTO 表B VALUES(:NEW.id,:NEW.type,:NEW.hitnum,1);
ELSIF UPDATING THEN
UPDATE 表B SET num = num + :NEW.hitnum WHERE ID =:NEW.id;
ELSIF DELETING THEN
DELETE FROM 表B WHERE ID =:NEW.id;
END IF ;
END ;

只是INSERT的话：

CREATE TRIGGER 表A_TRIG
AFTER INSERT OR UPDATE OR DELETE
ON 表A
FOR EACH ROW
BEGIN

INSERT INTO 表B 
SELECT ID,MAX(TYPE),SUM(hitnum),COUNT(1)
FROM 表A
WHERE ID = :NEW.id
GROUP BY ID;

END ;

类似这样？