1.序列方法：
==序列已创建的方法，CRUD
SQL> create sequence s8;
序列已创建。
SQL> select s8.nextval from dual;
NEXTVAL
----------
1
SQL> select s8.nextval from dual;
NEXTVAL
----------
2
SQL> select s8.nextval from dual;
NEXTVAL
----------
3
SQL> --查询默认数值
SQL> --切换到sys
SQL> show user;
USER 为 "SYS"
SQL> conn scott/tiger;
已连接。
SQL> --创建序列
SQL> create sequence s9;
序列已创建。
SQL> select * from user_seqence where sequence='S9';
SQL> select * from user_sequence where sequence_name='S9';
select * from user_sequence where sequence_name='S9'
*
SQL> select * from user_sequences where SEQUENCE_NAME='S9';
SEQUENCE_NAME MIN_VALUE MAX_VALUE INCREMENT_BY C O CACHE_SIZE
------------------------------ ---------- ---------- ------------ - - ----------
LAST_NUMBER
-----------
S9 1 1.0000E+28 1 N N 20
1
SQL> set lines 200
SQL> select * from user_sequences where SEQUENCE_NAME='S9'
2 /
SEQUENCE_NAME MIN_VALUE MAX_VALUE INCREMENT_BY C O CACHE_SIZE LAST_NUMBER
------------------------------ ---------- ---------- ------------ - - ---------- -----------
S9 1 1.0000E+28 1 N N 20 1