Unconnected Lookup Transformation In Informatica - Role Playing Date Dimension

Unconnected Lookup Transformation is a passive transformation since it can return only one column from each row to the return port. It is not connected to any other transformations in the mapping.

• It receives input from the result of a :LKP expression from transformations such as an Expression transformation or Aggregator transformation or Update Strategy Transformation.
• The Integration Service queries the lookup source or cache based on the lookup ports and condition in the transformation.
• The :LKP expression passes parameters to the Lookup transformation and receives a result back from the lookup.
• If there is no match for the lookup condition, the Integration Service returns NULL.
• You can call the Lookup transformation more than once in a mapping.
• Unlike Connected lookup, it can use only Static cache.

The main advantage of using an unconnected lookup is the fact that you can use it in any other transformation like a function  in other programming languages. The Lookup Cache is calculated only once as part of the session initialization and hence more efficient, since all subsequent look-ups will re-use the Cache.

The only constraint is that the cache has to be static, i.e. the data in your look-up table shouldn’t be changing once the lookup Cache has been created.

Scenario

Lookup Order Date, Due Date and Ship date in Date Dimension.

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