Tag Archives: subquery unnesting

Unnesting disjunctive subqueries (with OR predicate)

Jonathan Lewis has recently posted a good example of CBO not good enough in transforming specific query types. A recent thread on the SQL.ru Oracle forum reminded me of this issue.

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Scalar subquery unnesting

Here is a nice example of what Oracle is able to do with a subquery inside an expression. It can unnest it – that is a new feature of the transformation part of the CBO.

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