1. In a joiner transformation, you should specify the source with fewer rows as the master source. Why?
Joiner transformation compares each row of the master source against the detail source. The fewer unique rows in the master, the fewer iterations of the join comparison occur, which speeds the join process.
2. What is Lookup transformation?
It is used for looking up data in a relational table through mapping. Lookup definition from any relational database is imported from a source which has tendency of connecting client and server. One can use multiple lookup transformation in a mapping.
3. What is Incremental Aggregation?
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.
4. What is the function of Union Transformation?
The union transformation provides the use of multiple input groups that allows the transformation to process further.
It provides the data sources to be merged by using different sources and then the data is used in the application.
The pipeline consists of the data sources that are used for merging purpose and other union purposes.
The union transformations allow the transformations of the multiple input groups that provide merging of the data from different sources.
The transformation allows the use of functions like UNION ALL statements in SQL that combines with the result of the SELECT statements.
5. Design a mapping to load the first 3 rows from a flat file into a target?
Assign row numbers to each record. Generate the row numbers either using the expression transformation as mentioned above or use sequence generator transformation.
Then pass the output to filter transformation and specify the filter condition as O_count <=3