Posted by Erland Sommarskog on 04/23/06 13:46

David Portas (REMOVE_BEFORE_REPLYING_dportas@acm.org) writes:
> In your example you try to force a particular execution plan onto your
> code using an INDEX hint. But there is absolutely no reason why SQL
> Server should always be required to implement a hint. Indexes are
> intended as an optimization tool - they are not supposed to affect
> logical behaviour of code.

I only like to enforce this: if the result of a query is dependent on
the presense of an index, the result of the query is undefined (or there
is a plain bug). The task of indexes is to decrease execution times, but
they should not affect the outcome of a query.

Of course, by adding an index hint you at least ensure that they query
will fail would the index be dropped. Then again, if someone changes
the index, you lose anyway.



--
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
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