MDX Fundamentals Tutorial

This tutorial introduces the fundamental concepts of Multidimensional Expressions (MDX) for SQL Server Analysis Services. MDX is a query language used to retrieve data from OLAP cubes.

Introduction to MDX

Multidimensional Expressions (MDX) is the standard query language for Microsoft SQL Server Analysis Services. It's a powerful tool for analyzing data stored in multidimensional structures (cubes).

Core Concepts

Understanding the following core concepts is crucial for mastering MDX:

Dimensions and Hierarchies: How data is organized.
Measures: The numeric values you want to analyze.
Members: Specific elements within a dimension or hierarchy (e.g., '2023' in a 'Year' hierarchy).
Tuples: A set of members, one from each of a specified set of dimensions.
Sets: An ordered collection of tuples.

Basic MDX Syntax

An MDX query typically consists of the following clauses:

SELECT: Specifies the axes (rows and columns) of the query.
FROM: Specifies the cube or perspective to query.
WHERE: Filters the data by specifying a slicer.

Example: A Simple Query

Let's look at a basic MDX query to retrieve the 'Internet Sales Amount' for the '2023' year and the 'United States' country.

SELECT
    {[Measures].[Internet Sales Amount]} ON COLUMNS,
    {[Geography].[Country].&[United States]} ON ROWS
FROM
    [Adventure Works]
WHERE
    ([Date].[Calendar Year].&[2023])

Key MDX Functions

MDX provides a rich set of functions for manipulating data and performing complex calculations. Some common functions include:

[Measures].[Measure Name]: Refers to a measure.
[Dimension Name].[Hierarchy Name].[Member Name]: Refers to a specific member.
.CHILDREN: Returns the children of a member.
.PARENT: Returns the parent of a member.
.DESCENDANTS: Returns all descendants of a member.
SUM(): Aggregates values.
AVG(): Calculates the average.

Tip: Practice writing queries on a sample Analysis Services database to solidify your understanding.

Working with Sets

Sets are fundamental to MDX. They can be created using functions like { } for explicit members, () for tuples, and functions like { [Dimension].[Hierarchy].Members } or [Dimension].[Hierarchy].Children.

Example: Using a Set

SELECT
    { [Measures].[Internet Sales Amount], [Measures].[Internet Sales Quantity] } ON COLUMNS,
    { [Product].[Category].&[1], [Product].[Category].&[2] } ON ROWS
FROM
    [Adventure Works]

Next Steps

To continue your learning:

Explore more advanced MDX functions for calculations and aggregations.
Learn how to create calculated members and measures.
Understand MDX script and its role in Analysis Services.

Note: This tutorial covers the basics. For in-depth information, refer to the official SQL Server Analysis Services documentation.