--自動編號：Oracle
建表
create table t1(autoid number(10) primary key,name char(4));
創建序列
create sequence seq_t1_autoid;
添加數據
insert into t1(autoid,name) values(seq_t1_autoid.nextval,'a');
insert into t1(autoid,name) values(seq_t1_autoid.nextVal,'b');
commit;
--思考：能不能實現一個與DBMS無關的自動編號方法?
insert into t1(autoid,name) select max(autoid)+1,'c' from t1;
insert into t1(autoid,name)??select max(autoid)+1,'d' from t1;
commit;
--改正：
insert into t1(autoid,name) select nvl(max(autoid),0)+1,'c' from t1;
insert into t1(autoid,name)??select nvl(max(autoid),0)+1,'d' from t1;
commit;

面試：如何在Oracle中實現與Mysql一樣的自動編號：
解決：使用觸發器

create table t1(autoid number(10) primary key);
create sequence seq_t1_autoid;
create or replace trigger tr_t1_autoid
before insert on Friend
for each row
begin
??select seq_t1_autoid.nextval into :new.autoid from dual;
end;
--測試：
insert into t1(name) values('a');
insert into t1(name) values('b');
commit;
select * from t1;?

autoid? name??
?????1?? ? ?a????
?????2????? b????
+--------+------+