Oracle FAQ Your Portal to the Oracle Knowledge Grid
HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US
 

Home -> Community -> Usenet -> c.d.o.server -> Re: how to fetch the first n rows only for a query

Re: how to fetch the first n rows only for a query

From: Telemachus <telemachus_at_ulysseswillreturn.net>
Date: Thu, 25 Jul 2002 17:43:55 +0100
Message-ID: <fVV%8.4774$zX3.4331@news.indigo.ie>


Yes but as someone else pointed out use an inline query to get what you want

select abc from ( select <your query > order by blah ) where rownum < xyz

and yes, I agree, but when would it be important to retrieve this information in a relational framework ?

and I would regard the first record as the one with the earliest timestamp if there was one and so on...
"TurkBear" <jgreco1_at_mn.rr.com> wrote in message news:l060ku0bbqfg6p9mjorqr4c8kcngd8a2v1_at_4ax.com...
>
> One additional nitpick.
> .The rows returned by a where rownum < 25 ( or whatever)
> are, by no means, the FIRST 25 records in the database - The concept of
first or last ( or second or whatever number)
> is meaningless in a RDBMS - the 'order' in which rows are stored in not
determinate and may change ( probably will if many
> changes to the table are made)
> The rownum < 25 just limits the number or rows returned, nothing else.
>
> My 2c on one of my pet peeves....
>
>
> Fan Ruo Xin <fanruox_at_yahoo.com> wrote:
>
> >Thank you, Howard!
> >I did think they are the same thing. Thanks for your correcting me.
> >BTW, I am jsut curious when ORACLE introduce rownum?
> >Regards,
> >FRX
> >
> >"Howard J. Rogers" wrote:
> >
> >> Don't get too carried away... ROWID is not the same thing as ROWNUM at
all,
> >> and ROWID is still bad to use in a relational database, because you
have no
> >> control whatsoever over what rows get which rowids. And once assigned a
> >> rowid, a row always retains that same rowid (with one or two exceptions
> >> introduced in Oracle 8i). So a test on rowid<x.x.x.x would always
return
> >> exactly the same set of rows, regardless of what order by clause you
put in,
> >> or what changes you make to the data.
> >>
> >> But ROWNUM is assigned once a row has been selected. And that's why the
> >> 'ROWNUM<x' thing works.
> >>
> >> Regards
> >> HJR
> >>
> >> "Fan Ruo Xin" <fanruox_at_yahoo.com> wrote in message
> >> news:3D3E07EE.72CC7B8D_at_yahoo.com...
> >> > Thanks for the response from you all!!!
> >> > I always forget "rowid/rownum". I used to think "rowid" is not a good
idea
> >> > when you use SQL for relational DBMS. Now I chang my thinking.
> >> > Regards,
> >> >
> >> >
> >> > Fan Ruo Xin wrote:
> >> >
> >> > > Hi,
> >> > > I have a very simple query like,
> >> > > SELECT ...
> >> > > FROM MyTable
> >> > > WHERE
> >> > > ORDER BY
> >> > >
> >> > > Both the tablesize of mytable and result size are very big. I only
care
> >> > > the first 10 or 20 rows from the result set. How to implement it in
> >> > > ORACLE?
> >> > > BTW, I searched SELECT stmt in SQL Reference, got no help.
> >> > >
> >> > > Regards,
> >> > > Fan Ruo Xin
> >> >
>
>
>
> -----------== Posted via Newsfeed.Com - Uncensored Usenet News
==----------
> http://www.newsfeed.com The #1 Newsgroup Service in the World!
> -----= Over 100,000 Newsgroups - Unlimited Fast Downloads - 19 Servers
=----- Received on Thu Jul 25 2002 - 11:43:55 CDT

Original text of this message

HOME | ASK QUESTION | ADD INFO | SEARCH | E-MAIL US