OK. Let me give an example.

I have one tblEmployee table with EmployeeID as Primary Key and another column DepartmentID.

Another tblDepartment with DepartmentID as Primary Key and another column ManagerID as Foreign Key from the Employee table.

The column DepartmentID in tblEmployee is the foreign Key from the tblDepartment.

Now the above mentioned simple design is implementable and logical. If not, plz let me know. I am expecting many employees against one department. But One department will have only one manager and his ID is refered in the tblDepartment (this will be done by implemented logic).

Secondly, you are right, the logic to keep the tables related two ways should be coded properly. But still, the data in both tables is insertable independently (keeping the Foreign key column NULL).

Please correct me if I am wrong.