Tuesday, 3 February 2015

44 TOP etl interview questions and answers for experienced pdf (Part1)

1. When to use Abort, Decode functions?
Abort can be used to Abort / stop the session on an error condition. If the primary key column contains NULL, and you need to stop the session from continuing then you may use ABORT function in the default value for the port. It can be used with IIF and DECODE function to Abort the session.

2. What is constraint based loading ?
Constraint based loading. the data was loaded into the target table based on the Constraints.i.e if we want to load the EMP&DEPT data, first it loads the data of DEPT then EMP because DEPT is PARENT table EMP is CHILD table. In simple terms, it loads PARENT table first then CHILD table.

3. 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.

4. 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.

5. What is the default join that source qualifier provides?
Inner equi join.

6. What are the options in the target session of update strategy transformations?
Update as update
Update as insert
Update else insert
Truncate table

7. Which transformation should we use to normalize the COBOL and relational sources?
Normalizer Transformation.

8. What is the use of tracing levels in transformation?
Tracing levels store information about mapping and transformations.

9. What are the basic needs to join two sources in a source qualifier?
Two sources should have primary and foreign key relationships. Two sources should have matching data types.

10. What is update strategy transformation?
This transformation is used to maintain the history data or just most recent changes in to target table.
More Questions & Answers :-
Part1  Part2  Part3  Part4  Part5

No comments:

Post a Comment