Partial Dependency in DBMS

What is Partial Dependency?

Partial Dependency occurs when a non-prime attribute is functionally dependent on part of a candidate key.

The 2nd Normal Form (2NF) eliminates the Partial Dependency.

Let us see an example −

Example

<StudentProject>

In the above table, we have partial dependency; let us see how −

The prime key attributes are StudentID and ProjectNo, and

As stated, the non-prime attributes i.e. StudentName and ProjectName should be functionally dependent on part of a candidate key, to be Partial Dependent.

The StudentName can be determined by StudentID, which makes the relation Partial Dependent.

The ProjectName can be determined by ProjectNo, which makes the relation Partial Dependent.

Therefore, the <StudentProject> relation violates the 2NF in Normalization and is considered a bad database design.

To remove Partial Dependency and violation on 2NF, decompose the tables −

<StudentInfo>

<ProjectInfo>

Now the relation is in 2nd Normal form of Database Normalization.