Hi Ronald
On 20/08/2008, at 9:39 PM, Roland Bouman wrote:
Arjen, there is no logic reason to require that all non aggregate
expressions in the SELECT list are used in the GROUP BY.
"correctness" might be one ;-)
I do think it's on the same level as silent column changes, truncation
and lossy casting.
The true fix would be to only allow non-aggregate expressions in the
SELECT list that are functionally dependent upon the GROUP BY list
(and this would be in accordance with the 1999 and 2003 versions of
the SQL standard). However, I fear that this is not a trivial fix.
Yep that's what I was suggesting. I don't know how complex the fix
really is.
Sometimes bugs @ MySQL get noted as being more complex than they
really are, and it also relates to surrounding infrastructure which
Drizzle may not have to deal with. So what I was suggesting to Brian
is to look at it from this perspective, if it's not a highly complex
bug to fix, either fix it now or list it as a bug so that it will get
fixed.
If I am right that implementing this fix is too much trouble, then I
am in favour of allowing non-aggregate expressions in the SELECT list
even if they do not appear in the GROUP BY list, i.e. stick to MySQLs
current behaviour. Forcing full group by will make writing queries a
good deal more cumbersome, and will in addition lead to extra work in
executing the query (at least I assume that the query execution engine
is not smarter than the parser and is forced to take all specified
expressions in the GROUP BY into account, which to me is just a
performance penalty for no good)
Sure I agree with that.
I wouldn't want the ONLY_FULL_GROUP_BY behaviour as it is now.
Regards,
Arjen.
--
Arjen Lentz, Founder @ Open Query
Training and Expertise for MySQL in Australia and New Zealand
http://openquery.com.au/training/ (ph. +61-7-3103 0809)
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