Discuss how OLAP functionality is provided by the ROLLUP and CUBE functions of the SQL standard.
What will be an ideal response?
Aggregation is a fundamental part of OLAP. To improve aggregation capabilities the SQL
standard provides extensions to the GROUP BY clause such as the ROLLUP and CUBE
functions.
ROLLUP supports calculations using aggregations such as SUM, COUNT, MAX, MIN, and
AVG at increasing levels of aggregation, from the most detailed up to a grand total. CUBE is
similar to ROLLUP, enabling a single statement to calculate all possible combinations of
aggregations. CUBE can generate the information needed in cross-tabulation reports with a
single query.
ROLLUP and CUBE extensions specify exactly the groupings of interest in the GROUP BY
clause and produces a single result set that is equivalent to a UNION ALL of differently
grouped rows.
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