Introduction to Functional Dependency

Two clerks enter student records for the same college. One types roll number 101 with the name Alice Smith. The other types roll number 101 with the name Aliya Sharma.

Only one of them can be right. A roll number belongs to one student, so it cannot carry two different names.

That is a rule about the data itself. This chapter turns rules like it into something exact, so the database can check them and so you can decide, later, which tables need splitting.

The rule, stated in terms of rows

**A functional dependency says that one set of columns fixes the value of another set