Home » Oracle » 1z0-117 » Which query transformation technique is used in this scenario?
Examine the following query and execution plan:
Which query transformation technique is used in this scenario?
A. Join predicate push-down
B. Subquery factoring
C. Subquery unnesting
D. Join conversion
Correct Answer: A
Explanation/Reference:
*Normally, a view cannot be joined with an index-based nested loop (i.e., index access) join, since a view, in contrast with a base table, does not have an index defined on it. A view can only be joined with other tables using three methods: hash, nested loop, and sort-merge joins.
*The following shows the types of views on which join predicate pushdown is currently supported.
UNION ALL/UNION view
Outer-joined view
Anti-joined view
Semi-joined view
DISTINCT view
GROUP-BY view
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