Describe the four common OLAP operations for querying data. Provide an example of each operation using the OLAP cube in Figure 33.2.

Question

Answer 1

Common OLAP operations include:
(1) Roll-up, (2) drill-down, (3) slice and dice, and (4) pivoting.
Roll-up performs aggregations on the data by moving up the dimensional hierarchy or by dimensional
reduction e.g. 3-D to 2-D.
For example, {country, media and time} analysis of media streaming to {country, media} analysis of
streaming.
For example, analysis of weekly media streaming to analysis of monthly streaming.
Drill-down is the reverse of roll-up and involves revealing the detailed data that forms the aggregated
data. Drill-down can be performed by moving down the dimensional hierarchy or by dimensional
introduction e.g. 2-D to 3-D.
For example, {country, media} analysis of media streaming to {country, media and time} analysis of
streaming.
For example, analysis of monthly of media streaming to analysis of weekly streaming.
Slice and dice - ability to look at data from different viewpoints. The slice operation performs a
selection on one dimension of the data whereas dice uses two or more dimensions.
For example, a slice is analysis of media streaming according to {time = ‘2014’} OR {media = ‘film’}
OR {location = ‘London’}
For example, a dice is analysis of media streaming according to {time = ‘2014’} and {media = ‘film’}
OR {time = ‘2014’} and {media = ‘film’} and {location = ‘London’}
Pivot - ability to rotate the data to provide an alternative view of the same data.
For example, analysis of media streaming using the location (city) as x-axis against time (year) as the
y-axis can be rotated so that time (year) is the x-axis against location (city) is the y-axis.