How to test to ensure functionality does not change database state to more than what it intends

Specific scenario: - hundreds of student records in a database - invoke functionality to delete record of John Doe - functionality deletes John Doe's record but also incorrectly modifies Chris's

In a system scenario or even in a functional test scenario, how do we find this defect? How do we find what our software has done to the database in addition to what we intended for it to do? Even in a unit test, if we are only ensuring that John Doe's record has been deleted, we may not be able to find that Chris's record has been incorrectly modified. Code walkthrough or debugging by stepping through each line can identify.

What other ways are available to ensure correctness of the state of the database?