alter sequence modified from previous one, alter sequence, start with, oracle 10g , sql

1. 1DR. GIRIJA NARASIMHAN
Part 7- Alter Sequence

2. 2
DR. GIRIJA NARASIMHAN
Use the ALTER SEQUENCE statement to change the
increment,
minimum and maximum values,
cached numbers,
and behavior of an existing sequence.
This statement affects only future sequence numbers.

3. SQL> alter sequence seq1 start with 1001;
alter sequence seq1 start with 1001
*
ERROR at line 1:
ORA-02283: cannot alter starting sequence number
SQL> alter sequence seq1 increment by 2;
Sequence altered.
SQL> select seq1.nextval from dual;
NEXTVAL
----------
1001
SQL> select seq1.nextval from dual;
NEXTVAL
----------
1003
•If you change the INCREMENT BY value
before the first invocation of NEXTVAL, some
sequence numbers will be skipped.
•Therefore, if you want to retain the original
START WITH value, you must drop the
sequence and re-create it with the original
START WITH value and the new INCREMENT BY
value.
create sequence seq1
START WITH 1000
INCREMENT BY 1
NOCACHE
maxvalue 1005
minvalue 1000
cycle;
DR. GIRIJA NARASIMHAN

4. Oracle Database performs some validations. For example, a new
MAXVALUE cannot be imposed that is less than the current
sequence number.
SQL> select seq1.currval from dual;
CURRVAL
----------
1003
SQL> alter sequence seq1 maxvalue 1002;
alter sequence seq1 maxvalue 1002
*
ERROR at line 1:
ORA-04009: MAXVALUE cannot be made to be less than the current value
DR. GIRIJA NARASIMHAN

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