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Exercise No. 25: Cab Ride (log)

This cube stores data about people riding in a cab.

We have four dimensions with the following hierarchical structure:

Table L.E.51.1 - cab ride

"Km", "price" and "has luggage" are key figures.

Please draw the Classic Star and the Fact Constellation Schema. Then draw the dimension tables partitioned and normalized!

Solution

This case's Classic Star Schema has five tables, a central fact table and four dimension tables. The latter consist of a generated key as well as a key and a text field for each hierarchy (except the total aggregation) and the level attribute. The fact table uses the generated keys from the dimension tables as a combined key and contains three key figures ("km" and "price", "has luggage") in this example:

Figure L.E.51.1 - The Classic Star Schema

The Fact Constellation Schema for this case consists of four dimension tables and 24 fact tables (2x2x2x3):

Figure L.E.51.2 - The Fact Constellation Schema

Partitioning the Classic Star's dimension tables by the level attribute results in one table for each hierarchy level (in each dimension). All tables include the fields of the higher levels, the level attribute itself is omitted:

Figure L.E.51.3 - DT partitioned (left) and normalized (right)

Normalizing the dimension tables completely means that only the key of the next higher level is kept in each table. Please note that the tables for the total aggregation level have been neglected in Figure L.E.51.3.

This exercise is part of a case study: dfm - apa - log

Exercises List