It's not quite that simple because I'm really working with several tables and many queries. All of the demographic data does come from a common table of people. The key to almost everything is the ID field from that table. There are also tables of membership history that us ID as a foreign key, and the same for various bits of volunteer information. And of course, queries that, for everything up until now, pull the right data from the right tables to tell us information about members, volunteers, donors and other things. Some of the columns of new data that I needed for my new query make us of ConcatRelated to create strings from multiple records. In fact, there is one of those associated with members and one with volunteers.
So what I need can be described as follows:
Start with all the Member data.
Add those columns associated with Volunteer data.
Where the rows have the same ID, merge the data (some members are also volunteers).
Where there are rows with new IDs, add more rows.
Any ideas?