Oracle PL/SQL/Sequence/Sequence Increment

A decrement sequence

 
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>

Get next value from sequence

 
SQL> create table emp(
  2           emp_id                integer         primary key
  3          ,lastname               varchar2(20)    not null
  4          ,firstname              varchar2(15)    not null
  5          ,midinit                varchar2(1)
  6          ,street                 varchar2(30)
  7          ,city                   varchar2(20)
  8          ,state                  varchar2(2)
  9          ,zip                    varchar2(5)
 10          ,shortZipCode                   varchar2(4)
 11          ,area_code              varchar2(3)
 12          ,phone                  varchar2(8)
 13          ,company_name           varchar2(50));
Table created.
SQL>
SQL> create sequence s_emp_id
  2  start with 1000;
Sequence created.
SQL>
SQL> insert into emp (emp_id, lastname, firstname)
  2  values   (s_emp_id.nextval, "Einstein", "Albert");
1 row created.
SQL>
SQL> drop table emp;
Table dropped.
SQL>
SQL> drop sequence s_emp_id;
Sequence dropped.