Group by or Aggregate? for non numerical attributes

Hi Guys, me again, the newbie of RapidMiner.
There are 4 cities in the dataset and each city has multiple stores.
And I want to somehow group by the stores with the individual city.
Instead of:
City A, Store1
City A, Store2
City A, Store3
City B, Store4
....

I kinda want to have a form of: 
City A, Store 1
            Store 2
           Store 3
City B, Store 4
....

I hope it makes sense.
Could anyone help me with if there is an operator could achieve this?

Thanks again.