Generate New Attribute
I want to generate an attribute [AttNew]. The values of the new attribute should be according to the following rule:
- If ID xy only exist one time
- --> For ID xy Take the value of the Att1 for the new Attribute [AttNew]
- If there are several identical IDs,
- -> take all the values of Att 1 of the identical IDs
- --> and include them as a new attribute value for the generated attribute 
The reason behind that, I want to remove duplicate (or more) IDs but do not want to lose any information.
Below is the picture
Is there an operator which does that? Or can anyone help how to describe the function?
Thank you very much!