Need to Merge two databases without overwriting all fields
I have two databases of contacts. Some of the contacts are present in both databases, but not all. Each of the two databases has important information present only in that one database. I can't overwrite them, I need to merge the two together such that blank fields in one database are populated by the information in matching fields in the other, and vice versa. I have created a unique identifier for each record (lastname_firstname_city) to set as the index key (is that the term?). I'm okay with letting one database overwrite existing information in the other when that information is present in both databases. But it's the fact that each has important information in them that is lacking in the other database. I have over 2000 records, so doing this 'merging' of data one-by-one is a daunting task.
I'm pretty new to Filemaker, and a moderately good Excel user. I'm tempted to hire this out but don't know even how to do that!
Thanks in advance.