Multidimensional eXpressions is a language for expressing analytical queries. MDX is an extension to the SQL language which Microsoft utilizes to query and script access to multidimensional data. You can use MDX queries to get at data stored in a SQL Server Analysis Server cube by bringing back facts based on dimensions An MDX expression returns a multi-dimensional result set (dataset) that consists of axis data and cell data. expression syntax for querying multidimensional data in Microsoft SQL Server OLAP Services. Multidimensional Expressions (MDX) is a query language for OLAP databases, much like SQL is a query language for relational databases MDX is a query language that is used to interact and perform tasks with multidimensional databses (also called: OLAP Cubes). The MDX language was originally developed by Microsoft in the late 1990s, and has been adopted by many other vendors of Multidimensional Databases. A Multidimensional Database (also called: OLAP Cubes) is a method of storing data in a multidimensional form, generally for reporting purposes. In Multidimensional databases, data (measures) are categorized by Dimensions. Multidimensional databases are often pre-summarized across dimensions to drastically improve query time, over traditional Relational Databases. Microsoft's Multidimensional Database product is called SQL Server Analysis Services. In some ways we can draw an analogy between MDX and SQL. SQL is there to manipulate data; MDX is there to manipulate information. MDX started in a small company (Panorama) which was acquired by Microsoft, and hence it was seen for a while as a Microsoft standard. However, Microsoft relinquished control to a standards body and now MDX was adopted by Hyperion, which is now owned by Oracle. So MDX is now a non-proprietary standard.