Oracle-L: RE: dual

From: <Jared.Still_at_radisys.com>
Date: Thu, 30 Oct 2003 13:49:24 -0800
Message-ID: <F001.005D51AD.20031030134924@fatcity.com>

I encountered the same problem once many years ago, for the same reason.

Quite a pickle for a newbie - OWW bailed me out on that one. :)

Jraed

"M Rafiq" <rafiq9857_at_hotmail.com>
Sent by: ml-errors_at_fatcity.com
10/30/2003 12:29 PM
Please respond to ORACLE-L

        To:     Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
        cc: 
        Subject:        RE: dual

I have observed 2 rows in dual till version 7.3.4. All application using dual in their logic having more than 2 rows were giving wrong results. Quick
fix was to track it and delete more than one row(s). Duplicate import of sys/system stuff were known to be culprit.

Regards
Rafiq

Reply-To: ORACLE-L_at_fatcity.com
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Date: Thu, 30 Oct 2003 11:24:24 -0800

I have seen many databases crash, yes crash, when dual had more than one row
or less than one?

Why you say? As someone pointed out, this was an internal table to the kernel so Oracle used it as they felt. It was and still is considered a heartbeat mechanism within the kernel. In other words, don't mess with it.

Thank You

Stephen P. Karniotis
Technical Alliance Manager
Compuware Corporation

Direct:          (313) 227-4350
Mobile:         (248) 408-2918

Email: Stephen.Karniotis_at_Compuware.com
Web: www.compuware.com

-----Original Message-----

Sent: Thursday, October 30, 2003 2:05 PM To: Multiple recipients of list ORACLE-L

Do you think it will work if it has no rows ?

Waleed
-----Original Message-----

Sent: Thursday, October 30, 2003 1:44 PM To: Multiple recipients of list ORACLE-L

You may find this interesting.

Looks like a 'where rownum = 1' is always imposed on dual.

Same results on 8.1.7.4 and 9.2.0.4

Don't try this on anything other than a trashable test database.

Jared

10:42:04 dv03>@dt
10:42:05 dv03>
10:42:05 dv03>set echo on
10:42:05 dv03>
10:42:05 dv03>create table jkstill.dual as select * from sys.dual;

Table created.

10:42:05 dv03>
10:42:05 dv03>select * from jkstill.dual;

D
-

X

1 row selected.

10:42:05 dv03>
10:42:05 dv03>drop table jkstill.dual;

Table dropped.

10:42:05 dv03>
10:42:05 dv03>insert into sys.dual values('Y');

1 row created.

10:42:05 dv03>insert into sys.dual values('Z');

1 row created.

10:42:05 dv03>
10:42:05 dv03>commit;

Commit complete.

10:42:05 dv03>
10:42:05 dv03>select * from sys.dual;

D
-

X

1 row selected.

10:42:05 dv03>
10:42:05 dv03>create table jkstill.dual as select * from sys.dual;

Table created.

10:42:05 dv03>
10:42:05 dv03>select * from jkstill.dual;

D
-

X
Y
Z

3 rows selected.

10:42:05 dv03>
10:42:05 dv03>drop table jkstill.dual;

Table dropped.

10:42:05 dv03>
10:42:05 dv03>delete from sys.dual;

1 row deleted.

10:42:05 dv03>delete from sys.dual;

1 row deleted.

10:42:05 dv03>delete from sys.dual;

1 row deleted.

10:42:05 dv03>
10:42:05 dv03>insert into sys.dual values('X');

1 row created.

10:42:05 dv03>commit;

Commit complete.

10:42:05 dv03>
10:42:05 dv03>
10:42:05 dv03>create table jkstill.dual as select * from sys.dual;

Table created.

10:42:05 dv03>
10:42:05 dv03>select * from jkstill.dual;

D
-

X

1 row selected.

10:42:05 dv03>
10:42:05 dv03>drop table jkstill.dual;

Table dropped.

10:42:05 dv03>

<bulbultyagi_at_now-india.net.in>
Sent by: ml-errors_at_fatcity.com
10/30/2003 08:54 AM
Please respond to ORACLE-L

To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>

         cc:
         Subject:        dual

List, here is a rtfm question which I was scared to ask, but its bothering me too much so I just can't stay quite :

"why do multiple inserts into sys.dual complete sucessfully when connected as
sysdba, but a subsequent select * from dual show only 1 row ?"

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Author: M Rafiq
INET: rafiq9857_at_hotmail.com

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INET: Jared.Still_at_radisys.com

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