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Message Posted: Fri, 03 Oct 2002 @ 23:08:06 GMT

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Subj:   Re: Joins using varchar and char columns
From:   David Wellman


I can't see why it should, maybe you've hit a bug.

For example, a CHAR(10), a VARCHAR(30) and a CHAR(3) column each containing the same data value will generate the same hash value due to the way the hashing algorithm works. Certainly in the past I've run inner joins between different length CHAR columns (don't actually remember doing CHAR/VARCHAR columns) and the optimiser has recognised that rows to be joined are on the same AMP.

One thought. Are the character sets of the two columns the same? (i.e. both LATIN or both UNICODE). If not then that will almost certainly make a difference.



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