Oracle-L: RE: Creating sequences on the DUAL table?

From: Richard Huntley <rhuntley_at_mindleaders.com>
Date: Tue, 30 Jul 2002 10:59:54 -0800
Message-ID: <F001.004A643D.20020730105954@fatcity.com>

Sequences are DB objects independent of any tables including dual (not possible to create a sequence "on" a table. Sequences are sometimes used to populate the PK of a table, but the actual sequence and the table are not structurally related.

Such as:

SQL> create sequence myseq;

Sequence created.

Then, often developers will use the dual table when grabbing the next value from
the sequence.

SQL> select myseq.nextval from dual;

better to do this...insert into table1(id,name) values(myseq.nextval,'FName');

Check out the info in the docs on Sequences, maybe the concepts part would be a
good start.

HTH -----Original Message-----
Sent: Tuesday, July 30, 2002 1:54 PM
To: Multiple recipients of list ORACLE-L

I have a request from one of our developers to create two new sequences on the DUAL table.

This seems like a bad idea to me. I've never had such a request in the past. I asked for clarification on why this is needed and I didn't get a lot of details yet.

Is this something that is standard operating procedure? My understanding that interfacing with the DUAL table is usually inviting poor performance. Plus, I don't like to mess around with system tables, in general.

Under what circumstances would it be justified to create sequences on the DUAL table? Should I just flat-out refuse this request and if so, why?

Thanks,

Cherie Machler
Oracle DBA
Gelco Information Network

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Author: Richard Huntley
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