On 8/31/05, S. Isaac Dealey <[EMAIL PROTECTED]> wrote:
> >> > In Oracle, there is ROWNUM...
> >>
> >> Yeah, but that's not how you get a set out of the middle
> >> with Oracle,
> >> 'cause if you specify a minimum value for rownum you
> >> don't get the
> >> expected results... well... not by itself... In oracle
> >> you use the
> >> MINUS clause, which is surprisingly efficient... but... I
> >> still don't
> >> recommend using it, just because I advocate db
> >> independance.
> >>
> >> SELECT * FROM mytable WHERE rownum < 100
> >> ORDER BY my, column, list
> >>
> >> MINUS SELECT * FROM mytable WHERE rownum > 50
> >> ORDER BY my, column, list
>
> > note, the ORDER BY occurs after the WHERE clause, so this
> > may not give
> > the results you are expecting.
>
> I was lead to believe this was one of the uses the folks at Oracle had
> intended for the MINUS clause, and it did work when I needed it... I'm
> just thankfull I haven't needed it since then.
right. Its a matter of do you want
a) row 50 - 100 then sort them by mycolumn
or
b) sort by mycolumn then get row 50 to 100.
your example will handle a but not b. The rownum gets assigned prior
to ordering. Thinking about this, your example may not always get a
as expected since the rownum assignment may not be well defined.
Something like this works for b
SELECT * FROM (
SELECT a.*, rownum as rn FROM (
SELECT * FROM mytable ORDER BY mycolumn) a
) WHERE rn BETWEEN 50 AND 100
to get a definitively
SELECT * FROM (
SELECT a.*, rownum as rn FROM mytable a
) WHERE rn BETWEEN 50 AND 100
ORDER BY mycolumn
DK
>
> s. isaac dealey 954.522.6080
> new epoch : isn't it time for a change?
>
> add features without fixtures with
> the onTap open source framework
>
> http://www.fusiontap.com
> http://coldfusion.sys-con.com/author/4806Dealey.htm
>
>
>
>
>
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