Two tables(years), same structure, one relation, what function is used in this case?
Good morning. I have a problem to solve, if you can help me. I have two tables (different year: 2018-2019) with the same structure. I have two important variables in each of those tables : Clients and year. I want to identify two groups : The clients that come again in 2019 and classify them as continuators Customers who do not come in 2019 : classify them as lost. Any idea how? Thank you very much.