Re: Re: Rownum

From: Darrell Landrum <DLANDRUM_at_zalecorp.com>
Date: Wed, 19 Mar 2003 09:58:21 -0600
Message-Id: <24715.322386@fatcity.com>

That's correct, there's no rownum of 0.
ex.
SQL> select rownum, username from dba_users;

ROWNUM USERNAME

---------- ------------------------------
         1 SYS
         2 SYSTEM
         3 OUTLN
         4 OEM_DLAND
         5 DBSNMP
         6 HR
         7 PM
         8 DLANDRUM
         9 OE
        10 WMSYS
        11 ORDSYS
        12 ORDPLUGINS
        13 MDSYS
        14 CTXSYS
        15 QS_CS
        16 QS_CB
        17 QS_CBADM
        18 QS_OS
        19 QS_ES
        20 QS_WS
        21 QS
        22 QS_ADM
        23 SH
        24 XDB
        25 ANONYMOUS
        26 WKSYS
        27 WKPROXY
        28 ODM
        29 ODM_MTR
        30 OLAPSYS

30 rows selected.

I'm not sure what you mean by 'judge the select return', but the only real use I can think of for rownum is to restrict your query to a small random sampling of your data... ex.
SQL> select table_name, tablespace_name from dba_tables 2 where rownum < 5;

TABLE_NAME                     TABLESPACE_NAME
------------------------------ ------------------------------
SEG$                           SYSTEM
CLU$                           SYSTEM
OBJ$                           SYSTEM
FILE$                          SYSTEM

>>> liujd_at_cti.ac.cn 03/19/03 08:33AM >>>
Darrell Landrum,-? +úí

thanx for your explaination.
I wonder :whether i can judge the select return. I find the rowNUM is not 0, is right?

2003-03-19 05:03:00 -?+++ -++-- +ú =======

>Santosh,
>
>Good question. Actually these 2 are not related.
>Rowid is an actual attribute assigned to each row of a table and is unique.
>Rownum is logically assigned to rows returned in a query (nothing to do with the table). It is assigned sequentially as rows are returned (meaning if you can't have a rownum 2 until you've gotten a rownum 1).
>
>Ex.
>SQL> select rowid from dual;
>
>ROWID
>------------------
>AAAACsAABAAAAGkAAA
>
>SQL> select rownum from dual;
>
> ROWNUM
>----------
> 1
>
>SQL> select rownum from dual where rownum=2;
>
>no rows selected
>
>SQL> select rownum from dual where rownum < 2;
>
> ROWNUM
>----------
> 1
>
>
>Hope this was helpful,
>Darrell
>
>
>
>
>>>> vsantosh_at_psi.soft.net 03/19/03 03:43AM >>>
>Hello list,
>
> I wanted to know the concept of Rownum.. Is it similar to Row Id ?
>
>Thanks and Regards,
>Santosh
>
>
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íííííííííííííííííííí2003-03-19

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Received on Wed Mar 19 2003 - 09:58:21 CST