Merge Database

Hello! How are they? I ask you a question: I have a database of about 150,000 people, which contains at least their first name, their last name, their address and their national identification number. In addition, in some cases, you have other information such as your neighborhood, your email, your phone, etc. My question is: now I need to update that database and put a label in a column for some of those 150,000 people, which will then allow me to filter to that subgroup. The problem I have is that the system checks and finds, for example, various common names and automatically joins them, and checking the 150,000 one by one is not an option. It occurred to me, since it compares names and one more field, to put the national identification numbers in the phone column and create a separate column for phones. But I don't know how to do it in bulk, without having to re-import the entire database, which causes this merge problem that I mentioned (being that deleting it and starting from scratch is not an option either since many of these people already have comments and notes written by the team). Any suggestion is welcome! Thank you