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Posted by Erland Sommarskog on 04/24/06 13:57
(drawnai@hotmail.com) writes:
> Defined behaviour is as defined behaviour does. Outperforming an
> equivalent query ten to one is worth a rewrite 5 years from now, in the
> unlikely event that microsoft, remove the ability.
But the ability isn't there. It only looks like it is. That's why it's
undefined.
In SQL Server 6.5 GROUP BY implied an ORDER BY. Not so any more. In SQL 2000
people would put TOP 100 PERCENT ORDER BY in a view, and they found that
they did seem to need an ORDER BY when selecting from the view. In SQL 2005
more than one have found that they don't get away with it.
You get the result you get by happenstance. There is nothing that Microsoft
can remove, because they never added it. One day the optimizer decides to
do a different plan, and you don't get the result you wanted.
Of course, you may be prepared to take the gamble, but the day it breaks,
it's going to break hard.
--
Erland Sommarskog, SQL Server MVP, esquel@sommarskog.se
Books Online for SQL Server 2005 at
http://www.microsoft.com/technet/prodtechnol/sql/2005/downloads/books.mspx
Books Online for SQL Server 2000 at
http://www.microsoft.com/sql/prodinfo/previousversions/books.mspx
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