序列
--create sequence
create sequence empseq
increment by 10
start with 10
maxvalue 100
cycle--need cycle
nocache--needn't cache
--查询序列
select sequence_name,min_value,max_value,increment_by,last_number
from user_sequences
--查找下一个值
select empseq.nextval from dual
--查找当前值
select empseq.currval from dual
--修改序列[不能更改启动序列号]
alter sequence empseq
increment by 1
nocycle
nocache
--删除序列
--使用序列作为主键向表中插入值
insert into emp01
values(empseq.nextval,'AA',5500)
索引和同义词
--创建索引
create index emp01_id_ix
on emp01(employee_id)
--删除索引
drop index emp01_id_ix;
--创建同义词；
create synonym e for employees
select * from e
--删除同义词
drop synonym e;
