Scenario:
What is
aggregator transformation? & what is Incremental Aggregation?
Solution:
The
Aggregator transformation allows performing aggregate calculations, such as
averages and sums. Unlike Expression Transformation, the Aggregator
transformation can only be used to perform calculations on groups. The
Expression transformation permits calculations on a row-by-row basis only.
Aggregator
Transformation contains group by ports that indicate how to group the data.
While grouping the data, the aggregator transformation outputs the last row of
each group unless otherwise specified in the transformation properties.
Various
group by functions available in Informatica are : AVG, COUNT, FIRST, LAST, MAX,
MEDIAN, MIN, PERCENTILE, STDDEV, SUM, VARIANCE.
Whenever
a session is created for a mapping Aggregate Transformation, the session option
for Incremental Aggregation can be enabled. When PowerCenter performs
incremental aggregation, it passes new source data through the mapping and uses
historical cache data to perform new aggregation calculations incrementally.
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