You can not add a primary key constraint to views.
You can join columns though. In the join condition, you do not have to use a
primary key constraint.
FROM view1 v1
INNER JOIN view2
ON v1.vendor_id = v2.vendor_id
The type of join to use is based
upon your data requirement. In the example above, I am using an inner join. But
you'd have to tell us what you want in order for us to help.