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Oracle Data Warehouse Tuning for 10g
book

Oracle Data Warehouse Tuning for 10g

by Gavin JT Powell
April 2011
Intermediate to advanced content levelIntermediate to advanced
504 pages
16h 49m
English
Digital Press
Content preview from Oracle Data Warehouse Tuning for 10g
8.2
GROUP BY Clause Extensions 231
Chapter 8
,(i.industry)
)
It also follows that:
GROUP BY ROLLUP(l.city, i.industry)
is equivalent to:
GROUP BY GROUPING SETS
(
(l.city, i.industry)
,(l.city)
)
The ROLLUP and CUBE clauses perform internal UNION ALL set
operations between multiple query group aggregations. The GROUPING
Figure 8.15
GROUPING
SETS is not always
faster than CUBE.
232
8.2
GROUP BY Clause Extensions
SETS clause minimizes on the internal UNION ALL operations produced
by the ROLLUP and CUBE clauses. Therefore:
GROUP BY GROUPING SETS
(
(l.city, ...
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Publisher Resources

ISBN: 9781555583354