[Informatica] Rank Transformation

Rank Transformation

::Transformation type::

The Rank transformation allows you to select only the top or bottom rank of data.
You can use a Rank transformation to return the largest or smallest numeric value in a port or group. The Rank transformation differs from the transformation functions MAX and MIN, in that it allows you to select a group of top or bottom values, not just one value. As an active transformation, the Rank transformation might change the number of rows passed through it.
For example, you can use Rank to select the top 10 salespersons in a given territory

- The Rank port in Rank transformation is used to designate the column for which you want to rank values. You can designate only one Rank port in a Rank transformation. The Rank port is an input/output port. You must link the Rank port to another transformation.
- The Designer automatically creates a RANKINDEX port in the Rank transofrmation. This port is used by the PowerCenter to store the ranking position for each row in the group. The RANKINDEX is a output only port.
- You can enter the number of rows to select for the rank in Number Of Ranks input box in Properties tab.

::Ranking in Groups::
Like an Aggregator tranformation, Rank tranformation allows you to group the data and then apply Rank. For example, if you want to select the 10 most expensive items by manufacturer, you would first define a group for each manufacturer. To do this, you ned to check the Group By port in Rank Transformation.
Note that there can be multiple Group by ports and the order in which they appear in the transformation determines the Grouping and Ranking strategy.

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