SQL>
SQL> -- A decrement sequence
SQL>
SQL>
SQL> CREATE SEQUENCE StudentNumSeq
2 INCREMENT BY -1
3 START WITH 50000
4 MAXVALUE 99999
5 MINVALUE 0
6 NOCACHE
7 NOCYCLE;
Sequence created.
SQL>
SQL> select studentNumSeq.nextVal from dual;
NEXTVAL
----------
50000
SQL> select studentNumSeq.nextVal from dual;
NEXTVAL
----------
49999
SQL> select studentNumSeq.nextVal from dual;
NEXTVAL
----------
49998
SQL> select studentNumSeq.nextVal from dual;
NEXTVAL
----------
49997
SQL>
SQL>
SQL> drop sequence studentNumSeq;
Sequence dropped.
SQL>
SQL>
SQL>