CREATE TRIGGER ??????????
ON ????
{ FOR | AFTER | INSTEAD OF }
{ [ INSERT ] [ ?? ] [ DELETE ] [ ?? ]
   [UPDATE ] }
AS
  SQL ??? [ ... n ] 

???????????????

DROP TRIGGER ???????? [ ?? ... n ]

??????????????

ALTER TRIGGER ??????????
ON ????
{ FOR | AFTER | INSTEAD OF }
{ [ INSERT ] [ ?? ] [ DELETE ] [ ?? ]
   [UPDATE ] }
AS
  SQL ??? [ ... n ] 

?????????????

disable trigger trigDB on database --?????????
enable trigger trigDB on database --?????????


??????????????

print '??????????***'
raiserror('????????????'??16??1)
rollback transaction 

???????

??????S?????UPDATE????????

Create trigger tri_Updates
on s
for update
as
print 'the table s was updated'

??????????SC???г?????????????????

CREATE TRIGGER tri_del_grade
  ON SC FOR DELETE
  AS
    IF EXISTS(SELECT * FROM DELETED   
          WHERE Grade < 60)
      ROLLBACK 

???????SC???в???????????????????

create trigger tri_update_grade
on sc for update
as
  if update(grade)
  if exists(select * from inserted??deleted
  where inserted.sno=deleted.sno and inserted.grade>=60 and deleted.grade<60)
  begin
 print '?????????????????????'
  rollback
  end