# EXPRESSION TRANSFORMATION

1. WHAT IS AN EXPRESSION TRANSFORM?
2. HOW MANY TYPES OF PORTS ARE THERE IN EXPRESSION TRANSFORM?
3. WHAT IS THE EXECUTION ORDER OF THE PORTS IN AN EXPRESSION?
4. DESCRIBE THE APPROACH FOR THE REQUIREMENT. SUPPOSE THE INPUT IS:
5. HOW CAN WE IMPLEMENT AGGREGATION OPERATION WITHOUT USING AN AGGREGATOR TRANSFORMATION IN INFORMATICA?
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18. What is an Expression Transform?

Expression is a Passive connected transformation used to calculate values in a single row before you write to the target. We can use the Expression transformation to perform any non-aggregate calculations. We can also use the Expression transformation to test conditional statements before you output the results to target tables or other transformations.
For example, we might need to adjust employee salaries, concatenate first and last names, or convert strings to numbers.

19. How many types of ports are there in Expression transform?

There are three types of ports- INPUT, OUTPUT, and VARIABLE
20. What is the execution order of the ports in an expression?

• All ports are executed TOP TO BOTTOM in a serial physical ordering fashion, but they are done in the following groups:
• All input ports are pushed values first.
• Then all variables are executed (top to bottom physical ordering in the expression).
•  Last – all output expressions are executed to push values to output ports
You can utilize this to your advantage, by placing lookups in to variables, then using the variables “later” in the execution cycle.

21.Describe the approach for the requirement. Suppose the input is:  22.How can we implement aggregation operation without using an Aggregator Transformation in Informatica?

We will use the very basic concept of the Expression Transformation, that at a time we can access  the previous row data as well as the currently processed data in an expression transformation.
What we need is simple Sorter, Expression and Filter transformation to achieve aggregation at Informatica level.
For detailed understanding visit Aggregation without Aggregator.

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