It depends on what the result set you want should look like.
If Table 1 has every possible identifier in it, you can use a left join on that identifier in the "Multiple Tables" option. Start with the larger table, and left join Table 2 to it. You'll end up with all the rows from Table 1, with the rows that match the identifier in Table 2 being joined to the data. An inner join would result in only rows that match in BOTH tables. And a right join would be the opposite of the left join.
Data blending is a bit different, and has its own limitations and complications. If a JOIN will work, I'd go that route.
Someone can correct me if my descriptions are wrong. I'm still not an expert on joins, but I believe my descriptions are fairly accurate.
Thank you for your help Matthew! Would you only join on the unique identifier or on all the common columns?
I would need to know more about your dataset and what you are trying to accomplish to be able to answer that.
The description I gave above will be true for any fields you choose. So, for example, in my datasets, I often have an InstitutionID, and StudentID. I often perform various joins on these identifiers, because I want my result set to include records that match on both identifiers. if that makes any sense to you.
There's a lot of info out there on JOINS, as well as examples to study.
I hope this helps. If you still need assistance, you could randomize some of your data from both tables, and post them here for helpers to take a look at. We'd also need a description of what you are trying to accomplish, and what the resulting data should include.
Those articles were very helpful - thank you Matthew!