Data Warehouse Concepts - Data Warehouse Systems: Design and Implementation - page 66

RENAME(Sales, Customer.all → AllCustomers)

will rename the all member of the customer dimension.
The drill-across operation combines cells from two data cubes that have
the same schema and instances. The syntax of the operation is:

DRILLACROSS(CubeName1, CubeName2, [Condition])

The DRILLACROSS operation is analogous to a full outer join in the relational
algebra. If the condition is not stated, it corresponds to an outer equijoin.
Given the cubes in Fig. 3.4 a, h, the cube in Fig. 3.4 i is expressed by:

Sales2011-2012 ← DRILLACROSS(Sales2011, Sales2012)

Notice that a renaming of the cube and the measure, as stated above, is
necessary prior to applying the drill-across operation. Notice also that the
resulting cube is named Sales2011-2012 . On the other hand, if in the Sales
cube of Fig. 3.4 c we want to compare the sales of a month with those of the
previous month, this can be expressed in two steps as follows:

Sales1 ← RENAME(Sales, Quantity ← PrevMonthQuantity)

Result ← DRILLACROSS(Sales1, Sales, Sales1.Time.Month+1 = Sales.Time.Month)

In the first step, we create a temporary cube Sales1 by renaming the measure.
In the second step, we perform the drill across of the two cubes by combining
a cell in Sales1 with the cell in Sales corresponding to the subsequent month.
As already stated, the join condition above corresponds to an outer join.
Notice that the Sales cube in Fig. 3.4 a contains measures for a single year.
Thus, in the result above, the cells corresponding to January and December
will contain a null value in one of the two measures. As we will see in
Sect. 4.4 , when the cube contains measures for several years, the join condition
must take into account that measures of January must be joined with those
of December of the preceding year. Notice also that the cube has three
dimensions and the join condition in the query above pertains to only one
dimension. For the other dimensions, it is supposed that an outer equijoin is
performed.
The add measure operation adds new measures to the cube computed
from other measures or dimensions. The syntax for this operation is as follows:

ADDMEASURE(CubeName, (NewMeasure = Expression, [AggFct])* )

where Expression is a formula over measures and dimension members and
AggFct is the default aggregation function for the measure, SUM being the
default. For example, given the cube in Fig. 3.4 i, the measure shown in
Fig. 3.4 j is expressed by:

ADDMEASURE(Sales2011-2012, PercentageChange =
(Quantity2011-Quantity2012)/Quantity2011)

The drop measure operation removes one or several measures from a
cube. The syntax is as follows: