
SQL has the set operations union, intersect and except.

Find all customers having an account.
select distinct cname
from depositor

union: Find all customers having a loan, an account, or both.
branch.
(select cname
from depositor)
union
(select cname
from borrower)

intersect:
Find customers having a loan and an account.
(select distinct cname
from depositor)
intersect
(select distinct cname
from borrower)

except:
Find customers having an account, but not a loan.
(select distinct cname
from depositor)
except
(select cname
from borrower)

Some additional details:

union eliminates duplicates, being a set operation.
If we want to retain duplicates, we may use union all,
similarly for intersect and except.
 Not all implementations of SQL have these set operations.
 except in SQL92 is called minus in SQL86.
 It is possible to express these queries using other operations.