CrossJoin Rules in MDX Query

Question

I Want to Create an MDX Query Builder with javascript and I need a rules to check is query need for CrossJoin or Union . i find mdx-js but this library has not implement of CrossJoin so i want to Add this feature to `mdx-js.for example i have some dimension like this on columns:

COLUMNS: [Aircraft].[Aircraft Type].[Type]
         [Altitude].[Altitude]
         [Aircraft].[Aircraft Engines].[Engines]

so how to decide when write and use crossjoin or union.

Answer 1

Between different hierarchies and levels, you cannot use a Union is MDX, as all parameters to Union must have the same dimensionality. You could cross join these in case you want to see all combinations of these e. g. in the rows or columns.