Understanding multidimensionality

The following query is one of the simplest possible MDX queries:

--Query 5.1 
SELECT [Measures].[Sales Amount] ON COLUMNS
  FROM [Adventure Works DW2012];

As a seasoned SQL developer, you can see the similarities between SQL and MDX, the only thing in the previous query that shows that it is a MDX query is the ON COLUMNS keyword. However, there is a big difference between MDX and SQL. From now on, do not make any similarities between the T-SQL SELECT statement and the MDX SELECT statement they are totally different. MDX is a positional language, meaning that you position yourself in the multidimensional cube space through code.

What does this mean? The following figure shows a 3-dimensional cube. As you can see from the illustration, you have a dimension called Measures, a dimension called Time and a Product dimension. The previous query references one of the dimensions in the cube space ([Measures].[Sales Amount]) and places it on the column's axis.

The query...