As described previously, a set is an ordered collection of one or more tuples.
For example, in the following query, {[100-10]} is a set consisting of one tuple.
SELECT {[100-10]} ON COLUMNS FROM Sample.Basic
In the following query, {([100-10], [Actual])} is a also a set consisting of one tuple, though in this case, the tuple is not one member name. Rather, ([100-10], [Actual]) represents a tuple consisting of members from two dimensions, Product and Scenario.
SELECT {([100-10], [Actual])} ON COLUMNS FROM Sample.Basic
When a set has multiple tuples, the following rule applies: In each tuple of the set, members must represent the same dimensions as do the members of other tuples of the set. Additionally, the dimensions must be represented in the same order. In other words, each tuple of the set must have the same dimensionality. For example:
The following set consists of two tuples of the same dimensionality:
{(West, Feb), (East, Mar)}
The following set breaks the dimensionality rule, because Feb and Sales are from different dimensions:
{(West, Feb), (East, Sales)}
The following set breaks the dimensionality rule, because although the two tuples contain the same dimensions, the order of dimensions is reversed in the second tuple:
{(West, Feb), (Mar, East)}
A set can also be a collection of sets, or it can be empty (containing no tuples).
A set must be enclosed in braces {}, except in cases where the set is represented by an MDX function that returns a set.