请教一个oracle 触发器的问题

我想写这样一个触发器:表A中一行数据只要发生变化(增、删、改),就将这条数据更新到表B(同时将操作数据的时间也记录在表B中的时间字段),并在B中的标记字段中表明是发生了什么操作。谢谢各位达人了……

[code="sql"]

CREATE TABLE AA (
BT VARCHAR2(300)
);

CREATE TABLE TMP_LOG(
OPERATORTYPE VARCHAR2(20),
OPERATORTIME DATE,
BT VARCHAR2(300)
)

CREATE OR REPLACE TRIGGER TRIGGER_TMP
BEFORE INSERT OR UPDATE OR DELETE
ON AA
FOR EACH ROW
BEGIN
IF INSERTING THEN
INSERT INTO TMP_LOG(OPERATORTYPE, OPERATORTIME, BT)
VALUES( 'add',TO_CHAR(sysdate,'YYYYMMDDHH24MISS'), :NEW.BT);
ELSIF UPDATING THEN
INSERT INTO TMP_LOG (OPERATORTYPE, OPERATORTIME, BT)
VALUES( 'update',TO_CHAR(sysdate,'YYYYMMDDHH24MISS'), :NEW.BT);
ELSIF DELETING THEN
INSERT INTO TMP_LOG(OPERATORTYPE, OPERATORTIME, BT)
VALUES( 'delete',TO_CHAR(sysdate,'YYYYMMDDHH24MISS'), :NEW.BT);
END IF;
END TRIGGER_TMP;

[/code]