实验四 触发器的使用 4实验目的1、理解触发器基本概念。2、掌握触发器定义及其触发。3、了解触发器调试。4、理解触发器作用。实验内容1、定义一个触发器，完成及时计算所有供应商供应零件总数量。create or replace trigger t1_spjafter insert or delete or update on spjdeclarecursor cur_1 is select sno ,sum(qty) as sumqty from spj group by sno; begin for cur in cur_1 loop update s set sqty=cur.sumqty where s.sno=cur.sno; end loop; end t1_spj;insert into spj values(S5,P6,J4,700); 2、定义触发器，实现实体完整性（以s表供应商代码sno为例）。create or replace trigger t
