For your question... Or will I have a situation where the Join will pick up the first find?
The J output anchor will *never* pick up only the first record. It is not like an Excel VLookup. The Join tool will pick up every joined record from both input anchors.
suggestion: inside Alteryx, left-click on the Join tool, click the link for Open Example, run the Example, and study the outputs.
Beyond just the Join tool, for any analytic you will write, the first step is to truly know the input data. Use lots of investigative tools like Unique, Join, Summarize, etc to understand where duplicates exist and how data sets relate to each other.
If you join from table A to table B on City, State, and Zipcode, you will get duplicate records from table A if there are duplicates in Table B for the fields [City, State, Zip].
So attach a Unique tool to table B, and find out if there are duplicates. If you identify a duplicate, join from A to B, and look at the output for the duplicate you found in B. If the output isn't what you want, you'll have to figure out how to un-duplicate data in Table B, (but of course, only if the data in Table B can reliably be un-duplicated and give meaningful results).
Any analytic workflow, or any code in any programming language, is just telling the machine how you would perform a process manually. You have to understand the input data, from all tables, know how it's structured, understand the cardinality.
Chris
