Question

Illustrate how the process of creating first normal form relations may lead to mul. tivalued dependencies. How should the first normalization be done properly so that MVDs are avoided?

Short answer

The process of creating first normal form relations can lead to multi-valued dependencies, as multiple rows of data may be created for previously single-row values, leading to dependencies on a set of values. To avoid MVDs during the first normalization, separate the data into different tables based on a single theme, and link them together using a primary key.

Step-by-step solution

Understanding Database Normalization and First Normal Form

Database normalization is a process used to organize a database into tables and columns to reduce data redundancy and improve data integrity. The First Normal Form (1NF) is a level of database normalization where only scalar values are allowed. There are no set of values, repeating groups or arrays. A table is in 1NF if every cell contains a single value.

Understanding Multivalued Dependencies

A multivalued dependency (MVD) in a database is a type of functional dependency where an attribute in a relation depends upon another attribute in the same relation. In the case of a MVD, an attribute is dependent not just on a single value, but possibly set of values.

Illustrating 1NF Leading to MVDs

When converting a database to 1NF, you might create multiple rows of data to store values that were previously stored in a single row or column. These new tables can create Multivalued Dependencies. For example, consider a Student table where a student can have multiple hobbies and multiple languages. When converted to 1NF, this might lead to duplicate data for every combination of hobbies and languages, creating a MVD.

Avoiding MVDs during First Normalization

To avoid creating MVDs when you normalize to 1NF, separate the data into different tables based on a single theme. Using the previous example, instead of having a single Student table with both hobbies and languages, you can have a Student table, a Hobbies table, and a Languages table. Each of these tables would have a primary key (Student ID), that would link them together. By doing this, you avoid MVDs since each hobby or language aren't dependent on multiple students.

Key concepts

First Normal Form

First Normal Form, often abbreviated as 1NF, is a crucial step in organizing a database efficiently. The main goal of 1NF is to ensure that all the data in a table is atomic, which means that every field should hold the smallest possible unit of information. This eliminates repeating groups and arrays from the data tables.

When your database meets the criteria of 1NF:

• Each column contains only one value.
• All entries in a column are of the same type.
• Each column has a unique name.
• The order in which data is stored does not matter.

By ensuring that your tables are in First Normal Form, you set a strong foundation for further normalization steps that can further reduce redundancy and improve data integrity.

Multivalued Dependency

A multivalued dependency (MVD) can complicate database design and hurt performance if not addressed properly. MVD occurs when an attribute in a table is dependent on another attribute, but this dependency isn't exclusive to a single value, leading to multiple, often redundant tuples for each attribute combination.

To visualize this, imagine a student record where both 'Sports' and 'Languages' are stored together in a single table without being properly atomic. This might mean a student who plays multiple sports and speaks multiple languages results in multiple entries, duplicating other student information in every instance. Avoiding MVDs during initial database design ensures smoother data operations and less potential for inconsistency.

Data Redundancy

Data redundancy happens when the same piece of data exists in multiple places within a database. This typically leads to increased storage usage and can cause inconsistency problems during data updates. In the context of database normalization, one of the primary goals is to minimize redundancy.

Redundancy inflates the size of the database and can slow down queries. Furthermore, it can lead to anomalies when data has to be updated across numerous places. For instance, if a student's profile information appears in several tables, updating their contact information requires changes in multiple locations, risking inconsistencies and errors.

Normalizing data, especially through steps like 1NF, helps to streamline your database by eliminating such duplications, leading to more efficient and reliable data management.

Database Integrity

Database integrity ensures that the data is accurate and consistent throughout its lifecycle. Adopting normalization techniques such as First Normal Form plays a significant role in maintaining this integrity by ensuring that each data piece is stored only once.

There are several types of integrity that are crucial for databases:

• Entity Integrity: Each table must have a primary key, and every primary key value must be unique and not null.
• Referential Integrity: Foreign keys must accurately reference the corresponding primary keys in related tables.
• Domain Integrity: All columns in a database must adhere to predefined rules regarding the type and format of data they can hold.

Upholding these integrity rules ensures that the database remains a reliable and trustworthy resource, capable of avoiding the pitfalls of data anomalies and redundancy. This makes database operations smoother and more predictable.