Data Warehousing

Question 1

Data Warehouse

Answer 1

• Support database maintained separately from the operational database
• Consolidated, historical data for analysis
• Requires only data loading and data access

Question 2

Characteristics of a Data Warehouse

Answer 2

• Subject-oriented
• Integrated
• Time-variant
• Nonvolatile

Question 3

Populating a Data Warehouse

Answer 3

• Select data important for analysis
• Clear incomplete or inconsistent tuples
• Summarize values as necessary

Question 4

OLAP vs OLTP

Answer 4

• OLAP: on-line analytical processing
• OLTP: on-line transactional processing

Question 5

Applications of Data Warehouses

Answer 5

• Information processing
• Analytical processing
• Data mining

Question 6

Data Cube

Answer 6

• Multidimensional data model that provides summarizations for all subsets of dimensions

Question 7

Cuboids

Answer 7

• Summarizations along different dimensions of the data cube

Question 8

Base Cuboid

Answer 8

• The most detailed part of the data cube

Question 9

Apex Cuboid

Answer 9

• The highest level of summarization in the data cube

Question 10

Star Schema

Answer 10

• Consists of a central fact table connected to a set of dimension tables

Question 11

Snowflake Schema

Answer 11

• A refinement of star schema where some dimensional hierarchy is normalized

Question 12

Constellation Schema

Answer 12

• A collection of star schemas (multiple fact tables)

Question 13

Lattice

Answer 13

• A graph showing relationships between cuboids

Question 14

OLAP Slice

Answer 14

• Perform a selection on one dimension

Question 15

OLAP Dice

Answer 15

• Perform a selection on two or more dimensions

Question 16

Data Cube Summarization

Answer 16

• Remove a dimension
• Climb within a concept hierarchy
• Roll up (summarize)
• Drill down (generalize)

Question 17

Cuboids vs SQL GROUP BY

Answer 17

• Cuboids are equivalent to the results of GROUP BY operations