What are some examples of functional dependencies in databases?

What are some examples of functional dependencies in databases?

Functional dependencies are relationships between attributes in a database. For example, if we have a table of students with attributes like StudentID and StudentName, we can say that StudentID functionally determines StudentName. This means that for each StudentID, there is exactly one StudentName.

Can you give me another example?

Sure! Consider a table of orders with attributes OrderID, ProductID, and Quantity. Here, OrderID functionally determines ProductID and Quantity, meaning each OrderID corresponds to a specific ProductID and its Quantity.

What about composite keys?

Great question! In a table with attributes CourseID and StudentID, the combination of both can be a composite key that functionally determines the EnrollmentDate. This means that for each unique pair of CourseID and StudentID, there is a specific EnrollmentDate.

How do functional dependencies help in database design?

Functional dependencies help in normalizing databases, which reduces redundancy and improves data integrity. By understanding these dependencies, you can design tables that minimize duplication and ensure that data is logically organized.