Same with respect to what?
Your `jobnumber` is a name you've given to concat(year,month,idx), so in queries you can write something like ...
select x.this,y.that, ...
from table1 xx
join table2 y y on x.year=y.year and x.month=y.month and x.idx=y.iudx
...
... to retrieve other values that depend on that primary key.
Or you can make `jobnumber` a
derived column, read about that under Create table in the manual, then refer to it as if it were a single physical column.
You know, before trying to design a database for use, you need to read up on some basics of the tool you're using, eg ...
https://www.artfulsoftware.com/mysqlbook/sampler/mysqled1ch01.html
https://www.artfulsoftware.com/dbdesignbasics.html
This ain't like learning to ride a bicycle, there's a knowledge base without which you'll just make a mess that brings you trouble.