Why is Oracle's default sort different in these two databases?

Question

DB version: 10gR2
Schema: SCOTT
In one of our instance's Scott schema when i added a new row to emp table , the new row came at the top of the table.
insert into emp(empno,ename,job,mgr) values (8000,'Komal','Postman',32);
set lines 1000
set pages 70
select * from emp;
     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
      8000 Komal      Postman           32
      7369 SMITH      CLERK           7902 17-DEC-80        800                    20
      7499 ALLEN      SALESMAN        7698 20-FEB-81       1600        300         30
      7521 WARD       SALESMAN        7698 22-FEB-81       1250        500         30
      7566 JONES      MANAGER         7839 02-APR-81       2975                    20
      7654 MARTIN     SALESMAN        7698 28-SEP-81       1250       1400         30
      7698 BLAKE      MANAGER         7839 01-MAY-81       2850                    30
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    20
      7788 SCOTT      ANALYST         7566 19-APR-87       3000                    20
      7839 KING       PRESIDENT            17-NOV-81       5000                    20
      7844 TURNER     SALESMAN        7698 08-SEP-81       1500          0         30
      7876 ADAMS      CLERK           7788 23-MAY-87       1100                    20
      7900 JAMES      CLERK           7698 03-DEC-81        950                    30
      7902 FORD       ANALYST         7566 03-DEC-81       3000                    20
      7934 MILLER     CLERK           7782 23-JAN-82       1300                    20
15 rows selected.On another instance's Scott schema when i added a new row, the new row came at the bottom of the table.
insert into emp(empno,ename,job,mgr) values (8000,'Komal','Postman',32);
set lines 1000
set pages 70
select * from emp;
     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
      7369 SMITH      CLERK           7902 17-DEC-80        800                    20
      7499 ALLEN      SALESMAN        7698 20-FEB-81       1600        300         30
      7521 WARD       SALESMAN        7698 22-FEB-81       1250        500         30
      7566 JONES      MANAGER         7839 02-APR-81       2975                    20
      7654 MARTIN     SALESMAN        7698 28-SEP-81       1250       1400         30
      7698 BLAKE      MANAGER         7839 01-MAY-81       2850                    30
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10
      7788 SCOTT      ANALYST         7566 19-APR-87       3000                    20
      7839 KING       PRESIDENT            17-NOV-81       5000                    10
      7844 TURNER     SALESMAN        7698 08-SEP-81       1500          0         30
      7876 ADAMS      CLERK           7788 23-MAY-87       1100                    20
      7900 JAMES      CLERK           7698 03-DEC-81        950                    30
      7902 FORD       ANALYST         7566 03-DEC-81       3000                    20
      7934 MILLER     CLERK           7782 23-JAN-82       1300                    10
      8000 Komal      Postman           32
15 rows selected.What init.ora setting is making this difference? What should i do if i want the newly added row to come at the bottom of the table ?
Edited by: user659394 on Feb 10, 2009 10:37 PM

Answer 1

Oracle never guarantees that rows retrieved are sorted in any order.
If you need sorting, you must explicitly add the ORDER BY clause.
select * from emp order by empno;The "sequence" in which rows are presented to a client request can keep varying with the pattern of DELETEs and INSERTs and also how blocks are fetched from disk and also if a table get's rebuilt and also if an index is used and also if the query involves a join with one or more other tables etc etc