Expression transformations are used for row-wise manipulation. For any type of manipulation you wish to perform on an individual record, use an Expression transformation. The Expression transformation accepts the row-wise data, manipulates it, and passes it to the target. The transformation receives the data from the input port and sends the data out from output ports.

This is of type passive transformation which allows you to calculate the expressions for each record. An expression transformation in Informatica supports to write expression either in variable ports or only in output ports. In this Informatica Tutorial for Beginners, we will learn about Expression Transformation, it uses and examples. We will also learn about Rank Index and Rank Transformation in other posts.

Informatica Expression Transformation Uses
Use an Expression Transformation to derive the new attributes to change the inconsistent data into consistent format.

Use Expression Transformations for any row-wise calculation, such as if you want to concatenate the names, get the total salary, and convert it to uppercase

An expression transformation is created with following types of ports.

Input port (I)
Output Port (O)
Variable Port (V)
Variable Ports

A transformation variable is created by creating a port and selecting the V check box. When V is checked, the I and O check boxes are grayed out. This indicates that a variable port is neither an input nor an output port.Variables Ports are not visible in Normal view, only in Edit view.

1) Simplify complex expressions e.g. extract month from a date for use in several output ports
2) Provide temporary storage
3) Improve efficiency
4)Variables are initialized (numeric to 0, string to “”) when the Mapping logic is processed

Ports are evaluated in the order

1) All input ports
2) Variable ports in the display order (expressions can refer to input ports and variable ports that appear earlier in the port list)
3) Output ports (expressions can reference input and variable ports

Advanced Properties for Expression Transformation
Tracing Level Amount of detail that appears in the log for this transformation. You can choose terse, normal, verbose initialization, or verbose data. Default is normal.