MDX Function and Operator Reference - Professional SQL Server Analysis Services 2005 with MDX - page 1098

may have multiple members. If they have multiple members, it is possible
that more than one contributes to result tuples. Only the distinct tuples
from the dimensions listed in the first set-count sets will be returned,
though.
Note that if a measure field is NULL in the underlying fact table, Analysis
Services 2000 will treat the measure as zero, so the associated tuple will
show up in the nonempty set (unless all measures in the row are NULL).
Analysis Services 2005 allows measures to be NULLable, however, so
the tuple won't show up unless there actually was a value for it in the un-
derlying table.
Note that NonEmptyCrossJoin () always eliminates duplicate tuples, and
ignores all calculations by calculated members, cell calculations, MDX
scripts, and so on. This makes it less useful than NonEmpty () for de-
termining true non-emptiness of a set of tuples, so in general NonEmpty
() seems preferable.
See also: CrossJoin (), Extract (), Except (), Union (), Intersect ()
NOT expr Returns: Boolean Standard
The NOT operator returns false if expr is true, and false otherwise.
O
OpeningPeriod ([ level [, member ]]) Returns: member Standard
ClosingPeriod ([ level [, member ]]) Returns: member Standard
The OpeningPeriod () and ClosingPeriod () functions are essentially first-des-
cendant and last-descendant operators that are intended primarily to be used
with the Time dimension, though they may be used with any dimension. The
OpeningPeriod function returns the first member among the descendants of
member at level. For example, OpeningPeriod (Month, [1991]) returns [Janu-
ary, 1991]. If no member is specified, then the default is the current member
of the Time-type dimension in that cube. If no level is specified, then it is the
level immediately below that of member. OpeningPeriod (level, member) is
equivalent to Descendants (member, level).Item (0). ClosingPeriod () is very