那 REFERENCING OLD AS old NEW AS new 中的OLD old和NEW new是怎么回事?后面的new.列名又是怎么回事?和FROM dual中的dual是怎么回事?END后面的T_A_MemberShipID是怎么回事?谢谢! 请再帮我点清楚些!!
SQL> create sequence a_sequence 2 start with 1 3 increment by 1;序列已创建。SQL> create table t (n number ,v varchar2(10));表已创建。SQL> create or replace trigger t_trg 2 before insert or update on t 3 for each row 4 begin 5 select a_sequence.nextval into :new.n from dual; 6 end; 7 /触发器已创建SQL> insert into t values(111,'ok');已创建 1 行。SQL> select * from t; N V ---------- ---------- 1 ok
中的OLD old和NEW new是怎么回事?后面的new.列名又是怎么回事?和FROM dual中的dual是怎么回事?END后面的T_A_MemberShipID是怎么回事?谢谢!
请再帮我点清楚些!!
2 start with 1
3 increment by 1;序列已创建。SQL> create table t (n number ,v varchar2(10));表已创建。SQL> create or replace trigger t_trg
2 before insert or update on t
3 for each row
4 begin
5 select a_sequence.nextval into :new.n from dual;
6 end;
7 /触发器已创建SQL> insert into t values(111,'ok');已创建 1 行。SQL> select * from t; N V
---------- ----------
1 ok