Databases Reference
In-Depth Information
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fIGure 5.4
Driver Object.
is in an Itemset.” An object can be both the Driver and Correlation Object.
When an object is represented by the DRIVER_OBJECT_KEY, that object
is the Driver Object.
The DRIVER_QUANTITY and DRIVER_DOLLARS are metric mea-
surements for the transaction captured in the Itemset row. The metric
measurements in Figure 5.2 and Figure 5.4 are representative examples.
For any given Market Basket Analysis, the metric measurements could be
any that are applicable to the transactions being studied. The metric mea-
surements must be additive. They will be created by a summing operation.
They will be used within a summing operation. If a required metric is not
additive, such as a Yes/No or numeric, but nonadditive, code value, then
that measurement should be presented as a count of the occurrences of
the possible values of that metric. For example, a Yes/No metric would be
represented by a count of the occurrences of
Ye s
and a count of the occur-
rences of
No
.
The DRIVER_COUNT will be used to count the number of occurrences
of the DRIVER_OBJECT_KEY. Rather than ask the Market Basket Query
to sum and count records, the DRIVER_COUNT field provides the num-
ber 1 in each row, which allows the Market Basket Query to only sum the
numeric, additive value of the DRIVER_COUNT, which is 1. By summing
the DRIVER_COUNT, the Market Basket Query is counting occurrences
of the DRIVER_OBJECT_KEY.
correlation object
The Correlation Object is represented by the columns that begin with
CORR_, as shown in Figure 5.5.
The CORR_OBJECT_KEY identifies the object that performs the
function of a C orrelation Object. In the context of the Market Basket
Scope Statement, the CORR_OBJECT_KEY refers to “what Correlation
Object B is in, or not in, the Itemset?” An object can be both the Driver
