You should congratulate Paul, Thomas, he's probably the first user you
haven't been able to satisfy.
--
Kind reGards,
Gerard
(ghp_at_santens.be; ghp_at_skynet.be)
Paul Meurer <paul_at_hd.uib.no> schreef in artikel
<3447c70f.9107062_at_nntp.uib.no>...
> At 18:35 97/10/17 GMT, you wrote:
> >what you are doing is dangerous in a word.
> >
> >HINTS are just that, hints -- and they may be used, but then again, they
might
> >not. the first_rows hint is a very vague hint as well.
> >
> >ROWNUM is always evaluated BEFORE the aggregates ORDER and GROUP by are
applied.
> >When the below works for you it is because the index was used (in the
order by
> >search case) and the rows happened to have been read sorted. when it
"doesn't
> >work" (although technically it is in fact working as it should) it is
because
> >the rows are read not sorted, the rownum is applied, the first N rows
are taken,
> >and then sorted.
> >
>
> Thanks for your answer -- that's how I feared it would be, and it is
> totally logical. My appearently positive experiences with my first try
> led me to believe that it really would work that way. And then: why
> isn't the problem I want to solve addressed in some way? Of course it
> falls out of relational calculus proper, but many features of RDBSs
> do. For your solution is not what I want, I'm afraid. A user of the
> dictionary does not know beforehand which (how many) rows he is
> interested in, he wants to be able to scroll back and forth, but also
> jumps a lot. If I execute the query you suggest, I maybe get in return
> thousands of rows, at least on the server if I use a stored procedure,
> having to wait quite some time; of those rows the user reads two or
> three, only to issue a totally different query soon afterwards. (Maybe
> I am mistaken; I don't have to tell you that I am rather new to
> RDBSs.)
> Maybe I don't understand quite well how indices are working internally
> (I suppose they are B+-trees), but aren't they ordered and scanned
> alphabetically, and then, wouldn't it be easy to return the
> alphabetically first rows first?
>
> Yours, Paul
>
> Paul Meurer
> Norwegian Term Bank
> Allégaten 27
> N-5007 Bergen
> Norway
>
Received on Sun Oct 19 1997 - 00:00:00 CDT
