XML Map Grouping Methods

The XML Map transform groups output items in different ways depending upon the columns specified and whether or not aggregation functions are used.

Grouping method	Description
Simple grouping	The XML Map transform groups output items together according to the unique values of the grouping list when the following conditions are met: Source or target columns are specified in the grouping list If source columns are specified, no aggregation functions are defined in the selected target schema In this grouping method, no items are removed from the output data set.
Group aggregation	The XML Map transform performs exactly like a standard SQL GROUP BY clause when the following conditions are met: Source columns are specified in the grouping list Aggregation functions are defined in the selected target schema Columns in the aggregation functions descend from the sources in the current iteration rule Paths from the iterating sources to the columns do not contain any repeatable nodes Note All columns in the output schema must be either part of the grouping list or mapped to an aggregate function such as avg, count, max, min, or sum.
Instance aggregation	The XML Map transform evaluated the aggregation functions for each of the items in the output data set when the following conditions are met: Aggregation functions are defined under the selected target schema Columns used in the aggregation functions descend from the sources in the current iteration rule Paths from the sources to the columns being used contain repeatable nodes The XML Map transform also evaluates the aggregation functions for each of the items in the output data set when the following conditions are met: Aggregation functions are defined under the selected target schema Columns used in the aggregation functions descend from the selected target schema Paths from the selected target schema to the columns being used contain repeatable nodes

Grouping method

Description

Simple grouping

The XML Map transform groups output items together according to the unique values of the grouping list when the following conditions are met:

Source or target columns are specified in the grouping list
If source columns are specified, no aggregation functions are defined in the selected target schema

In this grouping method, no items are removed from the output data set.

Group aggregation

The XML Map transform performs exactly like a standard SQL GROUP BY clause when the following conditions are met:

Source columns are specified in the grouping list
Aggregation functions are defined in the selected target schema
Columns in the aggregation functions descend from the sources in the current iteration rule
Paths from the iterating sources to the columns do not contain any repeatable nodes

Note

All columns in the output schema must be either part of the grouping list or mapped to an aggregate function such as avg, count, max, min, or sum.

Instance aggregation

The XML Map transform evaluated the aggregation functions for each of the items in the output data set when the following conditions are met:

Aggregation functions are defined under the selected target schema
Columns used in the aggregation functions descend from the sources in the current iteration rule
Paths from the sources to the columns being used contain repeatable nodes

The XML Map transform also evaluates the aggregation functions for each of the items in the output data set when the following conditions are met:

Aggregation functions are defined under the selected target schema
Columns used in the aggregation functions descend from the selected target schema
Paths from the selected target schema to the columns being used contain repeatable nodes

Restriction

You cannot use both group and instance aggregation at the same time.