FYI, @Mike_P, just so you’re prepared for the huge differences between Oracle and Airtable, Airtable is a much more “simplistic” database program with almost NO automatic linking of records between tables.
And you cannot choose which fields you want to create linked relationships between. Every linked relationship is always a relationship to the record itself — not a specific field value in the record.
What you just experienced by converting a text field into a “linked record” field is one of the very few times when Airtable will “automatically” link records between tables for you. And that was just a “one time only” automatic linking during the conversion process.
But the vast majority of the time, all linked records must be explicitly & manually chosen by the user.
As I mentioned above, you’ll notice that all linked relationships ALWAYS link to the primary field in the other table. Meaning that you are always linking to an entire record, not a field value in that record.
The only other automatic linking that you will experience is if you paste in data into a “linked record field” and the value you just pasted exactly matches A PRIMARY FIELD VALUE in the other table. Then, an automatic link will be created to that other record. (And one cool trick is that Airtable will automatically create records in that other table if your pasted value doesn’t match any existing records.)
Hope this helps!! Airtable is super fun!!