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Message Posted: Mon, 31 Oct 2005 @ 15:23:37 GMT


     
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Subj:   Re: Skewed tables and VARCHAR column
 
From:   Geoffrey Rommel

          > select (count(*) (FLOAT)) /
          >   count(DISTINCT HASHROW (col1, col2...coln)) from TableA;

By the way, this query will not work on very large tables. There are only 2^32 = 4294967296 possible hash values, so if your table had, say, 6G rows and they were evenly distributed, this query would return 1.5.



     
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