Third normal form facts for kids

Third normal form (3NF) is a special way to organize information in computer databases. Think of a database as a super-organized collection of information, like a digital filing cabinet. Inside this cabinet, information is stored in tables, which are a lot like spreadsheets with rows and columns.

The goal of 3NF is to make sure your database tables are neat, easy to understand, and don't have repeated information. This helps prevent mistakes and makes the database work faster.

What is a Database?

A database is a structured collection of information. Imagine a library's catalog, but for computers! It stores all sorts of data, from customer names to product prices. This data is usually kept in tables.

Tables in a Database

A table in a database is like a grid. It has rows and columns.

• Each row is a single record or entry. For example, in a table of students, one row would be all the information about one student.
• Each column holds a specific type of information. For a student table, columns might be "Student ID," "Student Name," or "Grade."

Why Organize Data?

Organizing data in a database is called database normalization. It's like tidying up your room! When your room is organized, you can find things easily and avoid clutter. In a database, organizing helps:

• Avoid repeating data: No need to type the same information over and over.
• Prevent mistakes: If data is only stored once, there's less chance of errors.
• Make updates easy: Change information in just one place, and it updates everywhere.
• Save space: Less repeated data means the database takes up less storage.

What is Third Normal Form (3NF)?

Third normal form (3NF) is a rule for organizing tables. For a table to be in 3NF, it must follow two main rules:

1. It must already be in Second Normal Form (2NF). This means it's already pretty well organized, and all its columns depend on the main identifier of the row.
2. All columns that are not part of the primary key must depend only on the primary key. They should not depend on any other non-key column.

Understanding the Primary Key

A primary key is a special column (or set of columns) in a table. It uniquely identifies each row. Think of it like a student ID number. No two students have the same ID.

• If you know the primary key, you can find all the other information in that row.

No Transitive Dependencies

The most important part of 3NF is avoiding "transitive dependencies." This sounds complicated, but it just means:

• If column A determines column B, and column B determines column C, then column C "transitively depends" on column A.
• In 3NF, a non-key column (like C) should not depend on another non-key column (like B). It should only depend directly on the primary key (like A).

Let's look at an example:

Example: Student and Course Table

Imagine a table that stores information about students and the courses they are taking:

In this table:

• Primary Key: Student ID + Course ID (together, they uniquely identify each row).
• Problem: The "Teacher Name" depends on the "Course Name," not directly on the "Student ID" or "Course ID." If "Intro to Computers" is always taught by "Mr. Smith," then "Mr. Smith" depends on "Intro to Computers." This is a transitive dependency.

How to Make it 3NF

To fix this, we split the table into two smaller, more organized tables:

Now:

• In the "Student Table," "Student Name" and "Course ID" depend directly on "Student ID."
• In the "Course Details Table," "Course Name" and "Teacher Name" depend directly on "Course ID."

This way, "Teacher Name" no longer depends on "Course Name" in the same table. This makes the database more efficient and less prone to errors!

See also

In Spanish: Tercera forma normal para niños