I would like to keep all records when joining fields in ArcMap. I know that I could do this by adding a join, but I would like to use the Join Field tool so that I can dictate which fields are joined and so that it does not change the field name when joined. Is there a way to keep unmatched records when using the Join Field tool?
Using python, you could setup your code to specify the input tables and fields, in addition you could specify keep all fields. Here is the syntax table to refer to that uses the join field tool, that I found here or here and a detailed explanation on a another use by GIS SE user Polygeo here
or if you wanted to you can modify your code using the add join field as here
Here is the standard approach using the join data tool in ArcMap:
Once you have selected your files and fields to base your join on, you can keep all records by keeping the default radio button on "keep all records".
Esri, provide an overview on the essentials of joining a table here.
You can see the option here to keep all records, the features that joined and not. You will have null values in the fields with no corresponding match.