Sequence behavior

Question

Hi All,
I have come across one strange behavior of sequence in Oracle 11g R2. Could anyone please account for the change. I have posted the simulation scripts as below.
----Created a new sequence------
CREATE TABLE JO_SEQ_TEST (A NUMBER);
----Created a new table------
CREATE SEQUENCE JO_sEQ_1 START WITH 1;
----Populating the table with the sequence values------
DECLARE
M NUMBER;
BEGIN
FOR I IN 1..10
LOOP
DBMS_OUTPUT.PUT_LINE('Loop Count:'||TO_CHAR(i));
INSERT INTO JO_sEQ_TEST VALUES (JO_SEQ_1.NEXTVAL) RETURNING A INTO M;
DBMS_OUTPUT.PUT_LINE('Inserted value:'||TO_CHAR(M));
END LOOP;
END;
---block output-------
Loop Count:1
Inserted value:2
Loop Count:2
Inserted value:3
Loop Count:3
Inserted value:4
Loop Count:4
Inserted value:5
Loop Count:5
Inserted value:6
Loop Count:6
Inserted value:7
Loop Count:7
Inserted value:8
Loop Count:8
Inserted value:9
Loop Count:9
Inserted value:10
Loop Count:10
Inserted value:11
SELECT * FROM JO_SEQ_TEST;
2
3
4
5
6
7
8
9
10
11My question is that why the records are inserted starting with 2, and not with 1. How the sequence value 1 is missing during insertion?
If I try with alternative way, by holding the sequence value in another local variable, then inserting into the table, it works fine. Like below
---------after recreating the table and sequence------------
DECLARE
M NUMBER;
BEGIN
FOR I IN 1..10
LOOP
DBMS_OUTPUT.PUT_LINE('Loop Count:'||TO_CHAR(i));
M:= JO_SEQ_1.NEXTVAL;
INSERT INTO JO_sEQ_TEST VALUES (M);
DBMS_OUTPUT.PUT_LINE('Inserted value:'||TO_CHAR(M));
END LOOP;
END;
----block output-------
Loop Count:1
Inserted value:1
Loop Count:2
Inserted value:2
Loop Count:3
Inserted value:3
Loop Count:4
Inserted value:4
Loop Count:5
Inserted value:5
Loop Count:6
Inserted value:6
Loop Count:7
Inserted value:7
Loop Count:8
Inserted value:8
Loop Count:9
Inserted value:9
Loop Count:10
Inserted value:10

Answer 1

It appears that this is documented behavior:
http://stackoverflow.com/questions/4153807/oracle-sequence-starting-with-2-instead-of-1
(google rocks).