为什么显示触发器'AICHAT.BI_USERDATA'无效且重新验证失败为错误？

Question

CREATE TABLE  "USERDATA" 
   (    "USERDATAID" NUMBER, 
    "FNAME" VARCHAR2(4000), 
    "USERNAME" VARCHAR2(4000), 
    "PASSWORD" VARCHAR2(4000), 
    "CONTACTNO" VARCHAR2(4000), 
     CONSTRAINT "USERDATA_PK" PRIMARY KEY ("USERDATAID") ENABLE
   )

CREATE OR REPLACE TRIGGER  "BI_USERDATA" 
  before insert on "USERDATA"               
  for each row  
begin   
    select "USERDATA_SEQ".nextval into :NEW.USERDATAID from dual; 
end; 

/
ALTER TRIGGER  "BI_USERDATA" ENABLE
/

这是我创建表和触发器的代码，但它显示“'AICHAT.BI_USERDATA'无效，并且每当我尝试插入新值时都无法重新验证错误。这有什么问题？