Rank transformation

Rank transformation is used to get the top or bottom specific number of records. Consider that you need to take the top five salaried employees from the EMPLOYEE table; you can use rank transformation and define the property. A sample mapping indicating the Rank transformation is shown in the following screenshot:

When you create a Rank transformation, a default output port RANKINDEX comes with the transformation. It is not mandatory to use the RANKINDEX port. We have connected the RANKINDEX port to the target as we wish to denote the rank of the employees based on their SALARY.

When you use Rank transformation, you need to define the port on which you wish to rank the data. As shown in the following screenshot, we have ranked the data based on SALARY:

You cannot rank the data on multiple ports.

Also, you need to define either the Top or Bottom option and the number of records you wish to rank in the Properties tab. In our case, we have selected Top and 5 numbers to implement the scenario as shown in the following screenshot:

Rank transformation accepts the data in a row-wise manner and stores the data in cache. Once the data in received completely, it checks the data based on the condition and sends the data to the output port.

Rank transformation allows you to get the data based on a particular group. In the next section, we will talk about the group by key present in Rank transformation.