Re: Select random rows?

From: Connor McDonald <connor_mcdonald_at_yahoo.com>
Date: Fri, 05 Nov 1999 19:21:53 +0800
Message-ID: <3822BDD1.2972@yahoo.com>

fumi wrote:
>
> Connor McDonald <connor_mcdonald_at_yahoo.com> wrote in message news:382169BC.71E8_at_yahoo.com...
> > kev wrote:
> > >
> > > Hi,
> > >
> > > How do I select, say, 10 random rows from a dataset?
> > >
> > > - Kev
> >
> > (if your table is not too large...)
> >
> > select *
> > from ( select rownum each_row, a.*
> > from table a )
> > where each_row = xxx
> > and rownum < 10
> >
> > where 'xxx' is whatever appropriate random number generator you want
> > (eg dbms_random)
>
> This can not work.
> In Oracle8i, to random select, say, 5 random records from a table:
>
> SQL> execute dbms_random.initialize(dbms_utility.get_time());
>
> PL/SQL procedure successfully completed.
>
> SQL> select * from
> 2 (select * from emp order by dbms_random.random())
> 3 where rownum<=5;
>
> EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
> --------- ---------- --------- --------- --------- --------- --------- ---------
> 7934 MILLER CLERK 7782 23-JAN-82 1300 10
> 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
> 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
> 7876 ADAMS CLERK 7788 13-JUL-87 1100 20
> 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
>
> SQL> /
>
> EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
> --------- ---------- --------- --------- --------- --------- --------- ---------
> 7876 ADAMS CLERK 7788 13-JUL-87 1100 20
> 7788 SCOTT ANALYST 7566 13-JUL-87 3000 20
> 7782 CLARK MANAGER 7839 09-JUN-81 2450 10
> 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
> 7654 MARTIN SALESMAN 7698 28-SEP-81 1250 1400 30
>
> SQL> /
>
> EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
> --------- ---------- --------- --------- --------- --------- --------- ---------
> 7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300 30
> 7566 JONES MANAGER 7839 02-APR-81 2975 20
> 7839 KING PRESIDENT 17-NOV-81 5000 10
> 7844 TURNER SALESMAN 7698 08-SEP-81 1500 0 30
> 7782 CLARK MANAGER 7839 09-JUN-81 2450 10
>
> SQL> /
>
> EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO
> --------- ---------- --------- --------- --------- --------- --------- ---------
> 7900 JAMES CLERK 7698 03-DEC-81 950 30
> 7521 WARD SALESMAN 7698 22-FEB-81 1250 500 30
> 7902 FORD ANALYST 7566 03-DEC-81 3000 20
> 7566 JONES MANAGER 7839 02-APR-81 2975 20
> 7698 BLAKE MANAGER 7839 01-MAY-81 2850 30
Typo on my part...

The following WILL work (and you don't have to be on 8i to do it)...

SQL> create table test1 ( x number );

Table created.

SQL> insert into test1 select rownum from all_objects   2 where rownum < 999;

998 rows created.

SQL> commit;

Commit complete.

SQL> select *
  2 from ( select rownum xxx, a.* from test1 a)   3 where xxx in ( select random.rndint(500)

  4                 from test1
  5                 where rownum < 10 )

  6 /

      XXX X
--------- ---------

       15        15
       69        69
      133       133
      160       160
      167       167
      221       221
      338       338
      350       350
      450       450

9 rows selected.

SQL>
--

---

Connor McDonald
"These views mine, no-one elses etc etc" connor_mcdonald_at_yahoo.com

"Some days you're the pigeon, and some days you're the statue." Received on Fri Nov 05 1999 - 05:21:53 CST