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Message Posted: Wed, 29 Oct 2015 @ 00:37:31 GMT
| Subj: || || Re: SET vs MULTISET tables with UPI/USI |
| From: || || Pluebell, Fred |
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.