Are their ethical issues to consider when planning a database? For example, should personal data, such as medical information be stored in the same DBMS that manages employee salary and benefits data? Why or why not?

Yes

Explanation:

When planning a database, we must actually consider legal implications.

Let's say, a database of salary and all benefits of every worker in a company. Every one who is a worker in this company, either senior or junior worker can access this information in this database.

But in a case of more personal information like medical information, it would be wrong to make it accessible to all who have access to the database. Because it may cause issues like misuse of personal informations of others. Such an information in the hands of a wrong person may be used against someone with serious health conditions.

If information are stored separately, then it won't be accessible by just anyone and it would be better for all workers as no one would possess any information he or she is not supposed to have.