MDX Function and Operator Reference - Professional SQL Server Analysis Services 2005 with MDX - page 1068

Standard
Much like DrillDownMember (), this function returns a set that is formed
by drilling down one level on each member in set1 that is present in set2.
However, it returns the bottom index children for a parent rather than all
children. Set1 can be of arbitrary dimensionality; set2 must be of only
one dimension.
If set1 contains tuples, this will return a set that is formed by drilling down
each tuple in set1 that has a matching member from set2 in it. If
RECURSIVE is not specified, then only one pass through set1 is per-
formed, matching each member or tuple with each member in set2. If
RECURSIVE is specified, then the set that results from the first pass is
again matched with each member in set2 , and so on until no more mem-
bers in the set being constructed are found in set2. At each step of
drilling, the bottom index child members or tuples are returned instead of
all children. The ranking is based on the numeric expression , if specified;
otherwise, values from the set of children are evaluated in the current
context, and those results are used. Figure A-17 illustrates the behavior
of DrillDownMemberBottom ().
Figure A-17: DrillDownMemberBottom ().
DrillDownMemberTop ( set1 , set2 , index [, numeric expression ][,
RECURSIVE]]) Returns: set