Databases Reference
In-Depth Information
the Market Basket Analysis BI View. Without the keys, analysts using
the view will not be able to know the objects presented by the view. The
metrics, however, can be customized to suit the needs of a specific data
warehouse. The metrics provided in Figure 5.7 are fairly representative
of a common set of metrics. They can be modified to meet the source
data available in a data warehouse, or requirements of a Market Basket
Analysis application. The metrics of a Market Basket Analysis BI View
will be either additive or relative in nature. The relative metrics are built
using the additive metrics. When modifying the metrics of the Market
Basket Analysis BI View, metrics must be handled according to their
additive or relative properties. Otherwise, the results of the Market
Basket Analysis will be incorrect.
The second section of the Market Basket BI View isolates the Driver
Object and its metrics. The Market Basket Analysis BI View operates
against the Market Basket BI Table, which is an exploded representa-
tion of each Itemset so that the Market Basket BI Table can juxtapose
every occurrence of the Driver Object against every occurrence of the
Correlation Object. To reverse the exploded representation of the Itemset,
the Market Basket Analysis BI View retrieves the Driver Object in a sub-
select that includes a GROUP BY clause. Because an individual object that
can be the Driver Object can be the Driver Object in multiple Itemsets,
the ITEMSET_KEY is included in that GROUP BY statement. The result
is that the juxtaposed, and therefore repeated, statements of the Driver
Object are reduced to one statement of the Driver Object, which allows
the metrics of the Driver Object to represent only one iteration of the
Driver Object in an Itemset rather than
n
- 1 i terations of the Driver
Object.
The third section of the Market Basket Analysis BI View joins the
Correlation Object to the Driver Object. This is where the Driver
Object finally gets to drive. The join between the Driver Object and the
Correlation Object in the third section of the Market Basket Analysis BI
View places the Correlation Object into the context of the Driver Object.
This also multiplies again the number of rows containing the Driver
Object to
n
- 1 number of rows (where
n
= the total number of objects in
an Itemset). However, this join occurs without the recursive join of the
Market Basket Query in Figure 5.2.
The result set of the Market Basket Analysis BI View using the sample
data in this chapter is presented in Table 5.4.
