Gain insights into fundamental database concepts, relational databases, and entity-relationship diagrams. Learn about normalization techniques and basics of SQL to enhance database efficiency.

Databases are universal - they underlie the technology you use every day. They're a crucial component of everything from telecommunications systems, banking systems, and video games to just about any other software system that maintains some amount of persistent data.

In this course, you'll learn about the fundamental concepts of databases, why and when they're used, what relational databases are, and entity-relationship diagrams. You will also be exposed to techniques like normalization that help to increase the efficiency of databases. You'll wrap up with a look at the basics of Structured Query Language (SQL). 

After completing this course, you will be able to move onto more advanced courses involving database systems and SQL.

Database Design Fundamentals for Software Engineers

# Boyce-Codd normal form (BCNF)

For a table to satisfy the Boyce-Codd normal form, it should satisfy the following two conditions:

1. It should be in the third normal form.

2. And, for any dependency A → B, A should be a [super key](https://www.educative.io/courses/database-design-fundamentals/introduction-to-database-keys).

The second point sounds a bit tricky, right? In simple words, it means that for a dependency A $\rightarrow$ B, A cannot be a non-prime attribute if B is a prime attribute.


## Example

**ENROLMENT table**

| Std_Id    |  Subject   |  Professor   |
| --- | --- | --- |
|  101   |  CS-100   | Eddie Jessup    |
|  101   |  MATH-101   |  Charles Kingsfield    |
|  102   |  CS-100   | Robert Langdon    |
|  102   |  CHEM-101   |  John Keating   |
|  103   |  CS-100   |  Eddie Jessup  |


In the table above:

* One student can enroll in multiple subjects. For example, the student with `Std_Id` 101, has opted for two subjects: CS-100 and MATH-101.

* `Std_Id` and `Subject` together form the primary key as we can uniquely identify all the tuples in the table.

* One more important point to note here is that one professor teaches only one subject, but one subject may have two different professors. For example, CS-100 is taught by two different professors.

Hence, there is a dependency between the subject and professor where the subject depends on the professor's name.

This table satisfies the 1NF because all the values are atomic, column names are unique and all the values stored in a particular column are of the same domain.

This table also satisfies the 2NF as there is no partial dependency. There is also no transitive dependency, hence the table also satisfies the 3NF.

But this table is not in the Boyce-Codd normal form. The reason being that `Std_Id` and `Subject` form a composite primary key, which means `Subject` is a prime attribute.

But, there is one more dependency, `Professor`$\rightarrow$ `Subject`, and while `Subject` is a prime attribute, `Professor` is a non-prime attribute, which is not allowed by BCNF.

So, to make this relation (table) satisfy BCNF, we will decompose this table into two tables: the STUDENT table and the PROFESSOR table.

In this lesson, we will learn about Boyce-Codd normal form with the help of an example.

Introduction

Fundamental Concepts

Data Modeling

Entity-Relationship Data Model

The Relational Data Model

Functional Dependencies

Normalization

Structured Query Language

Conclusion

Boyce-Codd Normal Form

Boyce-Codd normal form (BCNF)