Querying Data Warehouses - Data Warehouse Systems: Design and Implementation - page 226

6.7 Review Questions
6.1 Describe what is MDX and what it is used for. Describe the two modes
supported by MDX.
6.2 Define what are tuples and sets and MDX.
6.3 Describe the basic syntax of MDX queries and describe the several
clauses that compose an MDX query. Which clauses are required and
which are optional?
6.4 Describe conceptually how an MDX query is executed by specifying
the conceptual order of executing the different clauses composing the
query.
6.5 Define the slicing operation in MDX. How does this operation differ
from the filtering operation specified in SQL in the WHERE clause?
6.6 Why is navigation essential for querying multidimensional databases?
Give examples of navigation functions in MDX and exemplify their use
in common queries.
6.7 What is a cross join in MDX? For which purpose is a cross join needed?
Establish similarities and differences between the cross join in MDX and
the various types of join in SQL.
6.8 What is subcubing in MDX? Does subcubing provide additional
expressive power to the language?
6.9 Define calculated members and named sets. Why are they needed?
State the syntax for defining them in an MDX query.
6.10 Why time series analysis is important in many business scenarios? Give
examples of functionality that is provided by MDX for time series
analysis.
6.11 What is filtering and how does this differ from slicing?
6.12 How you do sorting in MDX? What are the limitations of MDX in this
respect?
6.13 Give examples of MDX functions that are used for top and bottom
analysis. How do they differ from similar functions provided by SQL?
6.14 Describe the main differences between MDX and SQL.
6.8 Exercises
6.1 WriteinMDXthequeriesovertheFoodmartcubegiveninEx. 4.9 .
6.2 Consider the relational schema of the Foodmart data warehouse given
in Fig. 6.4 . Write in SQL the queries given in the previous exercise.