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

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
>> >

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