[Gretl-users] Append in cross-sectional data

Hello, I'd like to have some clarification on the line "b) that the new data carries clear observation information so that gretl can work out how to place the values" in the description of "append" from the Gretl Command reference. Basically, this is my situation: I have two databases. In both, I have a two fields "id1" and "id2". The combined fields are unique in the first database, while instead in the second I can have two different rows with the same "id1" and "id2" values. So, first question: when I append the second db to the first, are the common field names "clear observation information" for Gretl to do some sort of matching between the rows of the two databases? (as far as I can desume from my tests, the answer is "no", but I may be missing something) Second question: the second database has a field "days", and my aim is that in my merged database, the (unique) row with given "id1" and "id2" has, in the field "days", the sum of the "days" variable in all rows with that combination of ids. How can I do that? For whoever is familiar, I'm basically searching for an equivalent of STATA's "merge" (in the m:m case) and then "compact" commands. Thank you in advance for any hint Pietro