Rank Transformation

• Active and connected transformation

The Rank transformation allows us to select only the top or bottom rank of data. It Allows us to select a group of top or bottom values, not just one value.
During the session, the Power Center Server caches input data until it can perform The rank calculations.
Rank Transformation Properties :

• Cache Directory where cache will be made.
• Top/Bottom Rank as per need
• Number of Ranks Ex: 1, 2 or any number
• Case Sensitive Comparison can be checked if needed
• Rank Data Cache Size can be set
• Rank Index Cache Size can be set

Rank Index
The Designer automatically creates a RANKINDEX port for each Rank transformation. The Power Center Server uses the Rank Index port to store the ranking position for Each row in a group.
For example, if we create a Rank transformation that ranks the top five salaried employees, the rank index numbers the employees from 1 to 5.

• The RANKINDEX is an output port only.
• We can pass the rank index to another transformation in the mapping or directly to a target.
• We cannot delete or edit it.

Defining Groups
Rank transformation allows us to group information. For example: If we want to select the top 3 salaried employees of each Department, we can define a group for Department.

• By defining groups, we create one set of ranked rows for each group.
• We define a group in Ports tab. Click the Group By for needed port.
• We cannot Group By on port which is also Rank Port.