Aggregate functions perform operations on a set, or sequence, of input values. The input data for min, max, sum and avg is converted to the decimal data type for processing.
•The input values must be connected to the values parameter of the function.
•A context node (item) can be connected to the parent-context parameter to override the default context from which the input sequence is taken. The parent-context parameter is optional.
•The result of the function is connected to the specific target item.
The mapping shown below is available as Aggregates.mfd in the ...\Tutorial folder and shows how these functions are used.
Aggregate functions have two input items.
•values (nodes/rows) is connected to the source item that provides the data, in this case Number.
•parent-context is connected to the item you want to iterate over, i.e. the context, in this case over all Customers. The parameter is, however, optional.
The input instance in this case is an XML file containing the following data:
•The source data supplied to the values item is the number sequence 2,4,6,8.
•The output component in this case is a simple text file.
Clicking the Output tab for the above mapping delivers the following result:
min=2, max=8, count=4, sum=20 and avg=5.