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Message Posted: Mon, 08 Sep 2003 @ 13:08:07 GMT

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NUSIs are not hash redistributed and will result in an all-amp operation when searching for a party_id. A Hash Index, on the other hand, is effectively a duplicate of the original table (in your case a duplicate of only the fields party_id, acct_id and acct_src) that is re- keyed and therefore re-distributed by party_id.

Additionally, the Optimizer may choose to ignore a NUSI if the selectivity is low or statistics haven't been collected. If you intend to access more that the three fields in the Hash Index, then you may wish to include the ROWID, as this allows Teradata to jump to the original record in the base table for more values. Without it, Teradata may not used the Hash Index.

Jason

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