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Message Posted: Fri, 11 Feb 2005 @ 19:33:50 GMT
Bob Duell wrote:
Yes, unless the optimizer knows about uniqueness (unique/PK column or Union in subquery) there's an implict distinct.
Another case without distinct was described by Michael Larkins:
If the subquery is on NUPI column[s], the optimizer will probably choose an "inclusion merge join" and join only to the first occurance of a value.
Just Explain subqueries...
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