在线求助触发器

create or replace trigger inupdetable
  before update or delete or insert on table_a
  for each row
declare
  c number;
begin
--判断数据库内是否有数据
  select count(*) into c from table_b where id = :new.id;

--没有数据的操作
  if c = 0 then
       --插入
    if inserting then
      insert into table_b(id,username,age,createtime,sate)
      values
        (:new.id,
         :new.username,
         :new.age,
         sysdate,
         'I');
        
      --更新
    elsif updating then
      insert into table_b(id,username,age,updatetime,sate)
      values
        (:new.id,
         :new.username,
         :new.age,
         sysdate,
         'U');
        
       --删除
    elsif deleting then
      update table_b
         set username        = :old.username,
             age             = :old.age,
             deletetime      = sysdate,
             sate             = 'D'            
       where id              = :old.id;
    end if;
    
  --有数据的操作
  else
        --插入
    if inserting then
      update table_b
         set username        = :new.username,
             age             = :new.age,
             createtime      = sysdate,
             sate            = 'I'            
       where id              = :new.id;
       
       --删除
    elsif deleting then
      update table_b
         set username        = :old.username,
             age             = :old.age,
             deletetime      = sysdate,
             sate            = 'D'            
       where id               = :new.id;
       
       --更新
    elsif updating then
      update table_b
         set username        = :new.username,
             age              = :new.age,
             updatetime      = sysdate,
             sate            = 'U'
       where id              = :new.id;
       
    end if;
  end if;
end;