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Chapter 4 Tutorial.

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1 Chapter 4 Tutorial

2 Modeling Data Warehouse
A data warehouse is based on a multidimensional data model which views data in the form of a data cube A data cube allows data to be modeled and viewed in multiple dimensions Dimension tables Fact table contains measures and keys to related dimension tables

3 Cont. Star schema: A fact table in the middle connected to a set of dimension tables. Snowflake schema: represents dimensional hierarchy by normalizing the dimension tables. save storage reduces the effectiveness of browsing Fact constellations: Multiple fact tables share dimension tables

4 Q3 Suppose that a data warehouse consists of the three dimensions time, doctor, and patient, and the two measures count and charge, where charge is the fee that a doctor charges a patient for a visit. (a) Enumerate three classes of schemas that are popularly used for modeling data warehouses. Star schema Snowflake schema Fact constellation schema

5 Q3 cont. (b) Draw a schema diagram for the above data warehouse using one of the schema classes listed in (a). Using a star schema.

6 Q3 cont. Star Schema time Fact Table Measures time_key doctor_id
day day_of_the_week month quarter year time doctor_id doctor_name phone # address gender doctor Fact Table time_key doctor_id patient_id Charge Count patient_id patient_name phone # address gender patient Measures

7 Q5 Suppose that a data warehouse consists of the four dimensions, date, spectator, location, and game, and the two measures, count and charge, where charge is the fare that a spectator pays when watching a game on a given date. Spectators may be students, adults, or seniors, with each category having its own charge rate. Draw a star schema diagram for the data warehouse.

8 Q5 cont. Star Schema date Sales Fact Table date_id spectator_id
day month quarter year date spectator_id spectator_name phone # address Status Charge rate spectator Sales Fact Table date_id spectator_id location_id game_id Charge Count location_id phone # Street city province country location game_id game_name description producer game

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