Notes inline.
--
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk
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Mikito Harakiri wrote in message ...
>
>2. I don't quite understand why Jonatan associates the query
>
>where partition_col between a and c
>or partition_col between c and d
>
>to the "compare this year and last year". The latter is a selfjoin
query
>
>select a.*, b.* from sales a, sales b
>where a.year=1999 and b.year=2000
>and a.day=b.day -- day-by-day comparison
>
>which doesn't have any ORs in it, right?
>
Performance reasons -
The general case needs a full outer join (which probably
wasn't available when I wrote whichever note you found)
You also have to allow for oddities like the last two days
of the last week of last (financial) year being the first
two days of this (calendar) year, so the simple year
selection and day line-up doesn't work.
It does also depend on the capabilities of the front-end
tool that is presenting the data after selection, of course.
Received on Fri Dec 06 2002 - 08:35:14 CST
