This is undesirable, as should refer to a branch that exists.
Now suppose there is a tuple in the branch relation with ``Mokan'', but no matching tuple in the account relation for the Mokan branch.
This means that a branch exists for which no accounts exist. This is possible, for example, when a branch is being opened. We want to allow this situation.
In account, bname is a foreign key, being the primary key of another relation.