Multidimensional Expressions (MDX) has several elements that are used by, or influence, most statements:
Identifiers are the names of objects such as cubes, dimensions, members, and measures.
Define the types of data that are contained by cells, member properties, and cell properties. MDX supports only the OLE VARIANT data type. For more information about the coercion, conversion, and manipulation of the VARIANT data type, see "VARIANT and VARIANTARG" in the Platform SDK documentation.
Expressions are units of syntax that Microsoft SQL Server Analysis Services can resolve to single (scalar) values or objects. Expressions include functions that return a single value, a set expression, and so on.
Operators are syntax elements that work with one or more simple MDX expressions to make more complex MDX expressions.
Functions are syntax elements that take zero, one, or more input values, and return a scalar value or an object. Examples include the Sum function for adding several values, the Members function for returning a set of members from a dimension or level, and so on.
Comments are pieces of text that are inserted into MDX statements or scripts to explain the purpose of the statement. Analysis Services does not execute comments .
Reserved keywords are words that are reserved for the use of MDX and should not be used for object names used in MDX statements.
Members, tuples and sets are core concepts of multidimensional data that you must understand before you create an MDX query.