Retrieving Odd numbered rows from a table.

Question

In one recent interview I have been asked to write a SQL query to retreive Odd numbered rows from any table. At first I am confused on how to say whther a perticular row is odd or even. If it is based on rownum then rownum is not dynamic and every time the rownum changes for a perticular row. I finally used rowid for this puprpose, as you all of you know rowid is alphanumeric its not worked.
Can you please posta query to retrive odd numbered rows if its possible.

Answer 1

Mallik wrote:
In one recent interview I have been asked to write a SQL query to retreive Odd numbered rows from any table. At first I am confused on how to say whther a perticular row is odd or even. If it is based on rownum then rownum is not dynamic and every time the rownum changes for a perticular row. I finally used rowid for this puprpose, as you all of you know rowid is alphanumeric its not worked.
Can you please posta query to retrive odd numbered rows if its possible.As you say, if there's nothing in the data itself to offer a distinction as to what is "odd" and "even" then the closest thing is the rownum.
SQL> select * from (select rownum rn, emp.* from emp) where mod(rn,2) = 1;
        RN      EMPNO ENAME      JOB              MGR HIREDATE                    SAL       COMM     DEPTNO
         1       7369 SMITH      CLERK           7902 17-DEC-1980 00:00:00        800                    20
         3       7521 WARD       SALESMAN        7698 22-FEB-1981 00:00:00       1250        500         30
         5       7654 MARTIN     SALESMAN        7698 28-SEP-1981 00:00:00       1250       1400         30
         7       7782 CLARK      MANAGER         7839 09-JUN-1981 00:00:00       2450                    10
         9       7839 KING       PRESIDENT            17-NOV-1981 00:00:00       5000                    10
        11       7876 ADAMS      CLERK           7788 23-MAY-1987 00:00:00       1100                    20
        13       7902 FORD       ANALYST         7566 03-DEC-1981 00:00:00       3000                    20
7 rows selected.Anything else is making an assumption as to what is "odd" and "even". If it were me, the answer would be to do the above and also explain that, without any definition of what constitutes "odd" and "even" this is the closest possible, but not an accurate science as there is no guarantee as to the order of the records.