Data Warehousing
Matouš Havlena
matous@havlena.net
Big Data Analytics
UTC
Why data warehousing?
Data Information Decision
Data warehouse
Data warehouse is a database used for reporting and data
analysis. It is a central repository of data which...
Warehouse schemas - star
● Data in DW is arranged into hierarchical
groups called dimensions and into facts
● The simplest...
Warehouse schemas - snowflake
● Multiple dimensions
● Star and snowflake schemas are most commonly found in
dimensional da...
OLAP cubes
● Online Analytical Processing
● An approach to answering multi-dimensional
queries swiftly
● Represents star s...
Reports
Questions?
Thank you!
Matouš Havlena
matous@havlena.net
Data warehousing
Data warehousing
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What is data warehouse? DW layers, schemas, olap cubes?

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Data warehousing

  1. 1. Data Warehousing Matouš Havlena matous@havlena.net Big Data Analytics UTC
  2. 2. Why data warehousing? Data Information Decision
  3. 3. Data warehouse Data warehouse is a database used for reporting and data analysis. It is a central repository of data which is created by integrating data from one or more disparate sources. Data warehouse is a pool of historical data that doesn’t participate in the daily operations of the organization. Instead, this data is purposefully used for business analytics.
  4. 4. Warehouse schemas - star ● Data in DW is arranged into hierarchical groups called dimensions and into facts ● The simplest style of DW schema. ● Consists of one or more fact tables referencing any number of dimension tables. ● Special case of the snowflake schema, and is more effective for handling simpler queries.
  5. 5. Warehouse schemas - snowflake ● Multiple dimensions ● Star and snowflake schemas are most commonly found in dimensional data warehouses and data marts where speed of data retrieval is more important than the efficiency of data manipulations ● Don’t follow normal forms - speed tradeoff
  6. 6. OLAP cubes ● Online Analytical Processing ● An approach to answering multi-dimensional queries swiftly ● Represents star schema or snowflake schema in a relational data warehouse ● Each cell of the cube holds a number that represents some measure of the business, such as sales, profits, expenses, budget and forecast ● Measures are derived from the records in the fact table and dimensions are derived from the dimension tables ● Operations: Slice and Dice, Drill-up and Drill-down, Roll-up
  7. 7. Reports
  8. 8. Questions? Thank you! Matouš Havlena matous@havlena.net

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