borland Packages Class Hierarchy dx.dataset Package
java.lang.Object +----com.borland.dx.dataset.AggDescriptor
Constructors Properties Methods
Implements Serializable
The AggDescriptor
class collects the properties associated with an aggregation calculation. It is associated with a Column
by the Column
component's agg
property. In the JBuilder Inspector, this object is accessed from the agg
property. Selecting this property displays the Agg property editor where you can define the properties for your aggregate operation. This editor allows you to define:
Set the agg
property of a Column
component
to an instance of this class to define the type of aggregation to perform: count, sum,
minimum value or
maximum value. You specify a single column for the aggregation operation. You can optionally include a set of Column
names to base the grouping logic of the aggregation (subtotals) or, if left unspecified, the calculation is maintained across an entire DataSet
.
The update order of calc, lookup and aggregate columns is as follows:
calcAggAdd()
and calcAggDelete()
event handlers.
DataSet.addRow()
and DataSet.updateRow()
methods will be
modifed with the appropriate lookup values for any lookup columns they
may contain before the calcFields event is called.
The calcAggAdd
and calcAggDelete
event handlers are both called after
the non-calculated aggregates have been updated for add or delete
operations. An update operation is performed as a delete and then followed by an
add operation.
For more information on using aggregators in calculated columns, see
"Aggregating data with calculated fields" in the Database Application Developer's Guide.
For more information on the Agg
property editor, see the F1 Help topic Agg property editor.
For examples of applications that use aggregators, see the following projects in the specified directories of your JBuilder installation:
public AggDescriptor(String[] groupColumnNames, String aggColumnName, AggOperator aggOperator)Constructs an
AggDescriptor
object with the specified parameters.
groupColumnNames
Column
names that define the groups of rows to aggregate on.
aggColumnName
Column
to perform the aggregation on.
aggOperator
aggOperator
property for valid values.
public String getAggColumnName()Read-only property that returns the
Column
(by name) to perform the aggregation on.
public AggOperator getAggOperator()Read-only property that specifies the aggregation operation to perform. Valid values are:
SumAggOperator
MinAggOperator
MaxAggOperator
CountAggOperator
CustomAggOperator
class
public String[] getGroupColumnNames()Read-only property that returns the array of
Column
names that define the groups of rows to aggregate on.