Interview questions on aggregator transformation in informatica - Part -1

1. What is an Aggregator Transformation?
 
Answer:
 
An aggregator is an Active, Connected transformation which performs aggregate calculations like AVG, COUNT, FIRST, LAST, MAX, MEDIAN, MIN, PERCENTILE, STDDEV, SUM and VARIANCE.

2. How an Expression Transformation differs from Aggregator Transformation?
 
Answer:
 
An Expression Transformation performs calculation on a row-by-row basis, whereas an Aggregator Trans-formation performs calculations on groups.

3. Does an Aggregator Transformation support only aggregate expressions?
 
Answer:
 
Apart from aggregate expressions, aggregator transformation supports non-aggregate expressions and con-ditional clauses.


 

4. Give one example for each of Conditional Aggregation, Non-Aggregate expression and Nested Aggregation.
 
Answer:

Use conditional clauses in the aggregate expression to reduce the number of rows used in the ag-gregation. The conditional clause can be any clause that evaluates to TRUE or FALSE.

SUM (SALARY, JOB = ‘CLERK’)

 Use non-aggregate expressions in group by ports to modify or replace groups.

 IIF (PRODUCT = ‘Brown Bread’, ‘Bread’, PRODUCT)

Nested aggregation expression can include one aggregate function within another aggregate func-tion.

 MAX (COUNT (PRODUCT))