Communication gap and ignorance. The developers proably want to create new
sequences. And they are used to writing queries as "Select
sequencename.nextval from dual;" So they call it sequences on the dual
table.
"kkennedy"
<kkennedy@first To: Multiple recipients of list
ORACLE-L <[EMAIL PROTECTED]>
point.com> cc:
Sent by: Subject: RE: Creating sequences on the
DUAL table?
[EMAIL PROTECTED]
m
July 30, 2002
02:28 PM
Please respond
to ORACLE-L
Hmmmm? Sequences are not created "on" the dual table. Sequences exist as
independent entities. Ofttimes, sequence values are selected using the
dual table (e.g., select seqname.nextval from dual) -- this is a coding
choice. Performance of queries that select from the dual table are
generally not "inviting poor performance" (although I've seen some postings
on how to improve their performance).
If I were you, I would do some more reading up on sequences in the Concepts
manual and not worry too much about the performance. Suggest to the
developers that they use the sequences directly whenever possible rather
than selecting from dual as in the following:
One method:
select seqname.nextval into local_var from dual;
insert into destination_table (...id_column...) values (...local_var...);
Better method:
insert into destination_table (...id_column...) values
(...seqname.nextval...);
And, if the value is needed for other things:
insert into destination_table (...id_column...) values
(...seqname.nextval...)
returning id_column into local_var;
HTH
Kevin Kennedy
First Point Energy Corporation
If you take RAC out of Oracle you get OLE! What can this mean?
-----Original Message-----
Sent: Tuesday, July 30, 2002 10:54 AM
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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