XPost: comp.databases.oracle.misc, comp.databases.oracle.server   
   From: mcstockX@Xenquery   
      
   "Frank Piron"  wrote in message   
   news:opsf74act8m0et4w@news.online.de...   
   | Am Thu, 21 Oct 2004 09:37:42 -0400 schrieb Mark C. Stock   
   | :   
   | >   
   | >   
   | > did you try a standard UNIQUE constraint on the column?   
   | >   
   | > unlike SQL-Server (unless they've changed it since I last worked on it),   
   | > Oracle processes null values properly in this scenario (i.e., one NULL   
   | > value   
   | > is never consider equal to another NULL value)   
   |   
   | Yes, but it's a matter of convention because "NULL <> NULL" evaluates   
   | to null and thus is also not true. So two null values should never   
   | be considered different.   
   |   
   | > ++ mcs   
   | >   
   | >   
   |   
   | --   
   | Frank Piron,   
   | etfrankatkonaddotn   
   | (leftrotate two)   
      
   yes, in theory, the SQL Server approach is more 'pure', but in practice, the   
   Oracle approach is more practical (i'm starting to sound like yogi berra!)   
      
   if i'm creating a UNIQUE constraint, my goal is to disallow values that are   
   known to be equal to other known values -- so, it's entirely appropriate to   
   not disallow (sorry for the double-negs) unknown values (triple-negs?) since   
   there is no known basis for excluding them   
      
   ++ mcs   
      
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