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Message Posted: Mon, 07 Feb 2011 @ 19:19:56 GMT

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Subj:   Re: Which query will be faster ?
From:   DWellman


From (I think) TD 13 onwards #2 will be quickest as it doesn't read every row. TD will answer this query using the cylinder index structure. Physically smaller, fewer io's so faster.

#1 will be slowest.

I think #3 and #4 will be about the same because the plan will be the same. In both cases the AMP/file system basically says "you only want 'n' rows", I'll stop when I've returned that number". Have you tried checking the explain plan for these two ?

All of the above assumes of course that you're not talking about a small table :-)



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