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Message Posted: Thu, 02 Dec 2004 @ 15:18:06 GMT

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Nazy:

You didn't provide any details on which statistics you collected, ie. column, index, or multi-column.

Is it possible you used the newest multi-column collection? I ask because I tried this and got much different results than I anticipated. When I ran my EXPLAIN afterward, it indicated that I would access 354 rows with high confidence. However, there were only 9 rows in the table. I believe there were probably 354 different combinations of the values in these columns, but certainly not that many rows. Once I dropped these statistics and collected on the single column my EXPLAIN went back to 9 rows with high confidence.

It would appear that multi-column statistics have a place in the arsenal of Teradata tools. However, it does not appear that it is to replace mulitple runs of the collect statistics command.

Again, I do not know if this is what happened to you; it is only my guess from prior experience. If this is not true and you want someone to provide you a more definitive answer, you might post more details regarding what you actually did pretaining to collecting and the SQL that is now running longer.

Regards,

Michael Larkins
Certified Teradata Master
Certified Teradata SQL Instructor

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