oracle触发器用于操作过一个表要对另一个表产生影响，这是可以用触发器
比如记录谁更新过这个记录等
---------------------------------------
Create Or Replace Trigger huiTrig
After Insert Or Delete Or Update On dept For Each Row
Begin
If Inserting Then
Insert Into emp Values (999,'insert', 0);
Elsif Updating Then
Insert Into emp Values (999,'update', 0);
Elsif Deleting Then
Insert Into emp Values (999,'delete', 0);
End If;
End;