The Lookup transformation
The Lookup transformation is used to look up a source, source qualifier, or target to get the relevant data. You can look up flat file and relational tables. The Lookup transformation works on similar lines as the joiner, with a few differences. For example, lookup does not require two sources. Lookup transformations can be connected and unconnected. They extract the data from the lookup table or file based on the lookup condition.
Creating a Lookup transformation
Perform the following steps to create and configure a Lookup transformation:
In Mapping Designer, click on Transformations and create a Lookup transformation. Specify the name of the Lookup transformation and click on OK.
A new window will ask you to select Source, Target, or Source Qualifier that you wish to look up. You will get a list of all the sources, targets, and source qualifiers available in your repository. Click on the required component and then click on OK, as shown in the following screenshot...