Relating data without a primary key

I'm wondering if the way I relate data in tables that are related, but dont have a primary/foreign key is correct. 

In the image below there are three SQL tables and a View (Submission_Scores).
The first threee tables have keys I can directly relate. 

Site is a list of locations

Site items is a static list of items that needs to be scored against each month
Submissions is the actual scores against the site items. These are reported each month, and has a year and month column. 

The fourth table is a SQL view that takes the submissions values, and performs some complex calculations to give scores per category and an overall score. 

What I've done is create a calulated column in submissions and submissions scores that takes the site name, year, and month into a string. Then used that column to relate the tables. 

Is this the correct way to do it, or is there a better way?