1 ALTER SEQUENCE sequence_name INCREMENT BY number;
ex: ALTER SEQUENCE myseq INCREMENT BY 1; ---> add 1 to last number;
ex: ALTER SEQUENCE myseq INCREMENT BY -1; ----> subtrace 1 from last number;
2 select myseq.currval from dual; ---> sequence current number
select myseq.nextval from dual; ---> sequence next number
3 修改sequence 的cache為0.
ex: ALTER SEQUENCE sequence_name NOCACHE
