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Message Posted: Thu, 29 Oct 2015 @ 21:04:24 GMT


     
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Subj:   Re: SET vs MULTISET tables with UPI/USI
 
From:   Anomy Anom

<-- Anonymously Posted: Thursday, October 29, 2015 16:39 -->

Fred Pluebell wrote:

  The duplicate row checking is still done, but with a UPI you only have to check at most one row so the overhead is tiny. With NUPI, the overhead can be substantial even with a USI.  


  If you have a SET table with a UPI or USI, then multiple-row operations (e.g. INSERT SELECT or MERGE) will quietly eliminate duplicate rows , whereas with MULTISET table and UPI or USI, the duplicate key check will cause the operation to fail. For single-row operations (e.g. INSERT VALUES), SET/MULTISET both give duplicate key error.  


So to narrow this down - for SET tables with UPI/USI, TD will check only the UPI/USI column(s) for duplicates and entire row (all columns) checking will not be done ?


Thanks



     
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