Working with Lookup

Lookup is a passive transformation which accept parameters and returns one ore more columns in result. There are different types of lookup transformations like
1. Connected Cached Lookup ( Also referred as Static lookup)
2. Connected Uncached Lookup
3. Unconnected Cached Lookup
4. Unconnected Uncached Lookup
5. Dynamic Lookup

The same lookup transformation can be changed to Cached/uncached/dynamic based on the property selected.




Connected Cached Lookup

As name suggest, this transformation is in the flow of each row and input and output port is connected to other transformation in the mapping. This lookup can return more than one column in the result.
Characteristics of Connected Lookup

1. A connected Lookup transformation receives input values directly from another transformation in the pipeline.
2. For each input row, the PowerCenter Server queries the lookup source or cache based on the lookup ports and the condition in the transformation.
3. If the transformation is uncached or uses a static cache, the PowerCenter Server returns values from the lookup query.
4. The PowerCenter Server passes return values from the query to the next transformation.

Characteristics of Unconnected Lookup

An unconnected Lookup transformation receives input values from the result of a :LKP expression in another transformation. Unconnected Lookup transformation can be called more than once in a mapping.

1. An unconnected Lookup transformation receives input values from the result of a :LKP expression in another transformation, such as an Update Strategy transformation.
2. The PowerCenter Server queries the lookup source or cache based on the lookup ports and condition in the transformation.
3. The PowerCenter Server returns one value into the return port of the Lookup transformation.
4. The Lookup transformation passes the return value into the :LKP expression.