Describe the characteristics of a table in Unnormalized Form (UNF) and describe how such a table is converted to a First Normal Form (1NF) relation. What is the minimal normal form that a relation must satisfy? Provide a definition for this normal form. Describe the two approaches to converting an Unnormalized Form (UNF) table to First Normal Form (1NF) relation(s).
The Correct Answer and Explanation is :
Characteristics of a Table in Unnormalized Form (UNF)
A table is in Unnormalized Form (UNF) when it contains repeating groups or nested relations. Characteristics include:
- Repeating Groups: A single cell contains multiple values (e.g., lists or arrays).
- Non-Atomic Values: Data in some columns is not atomic, meaning it cannot be broken down further.
- Lack of Clear Structure: There may not be distinct rows for each record, leading to data redundancy and difficulty in processing.
Conversion from UNF to First Normal Form (1NF)
A table is converted from UNF to First Normal Form (1NF) by:
- Eliminating Repeating Groups: Ensure that every column contains atomic (indivisible) values.
- Creating Unique Rows: Each row must represent a unique record.
- Adding Primary Keys: Introduce a unique identifier for each row if one does not already exist.
Minimal Normal Form for a Relation
The minimal normal form a relation must satisfy is First Normal Form (1NF).
Definition of 1NF: A relation is in 1NF if:
- All attributes contain atomic values.
- Each column contains values of a single type.
- The table does not have repeating groups.
Approaches to Converting UNF to 1NF
- Flattening the Table:
- Split repeating groups into individual rows.
- Ensure that each row has atomic values.
- Add a primary key (if necessary) to uniquely identify each row.
- Splitting into Related Tables:
- Divide the UNF table into multiple related tables.
- Ensure each table is in 1NF.
- Establish relationships between tables using foreign keys.
Explanation (300 Words)
A table in Unnormalized Form (UNF) lacks proper relational structure. For example, a cell containing a list of phone numbers violates the rule of atomicity. Such tables are prone to redundancy, inconsistency, and difficulty in querying. To address this, conversion to First Normal Form (1NF) is required. This involves ensuring that every value in every column is atomic and no repeating groups exist.
The first step is flattening the table, where repeating groups are expanded into individual rows. For instance, if a cell contains multiple phone numbers, each number is placed in its own row, paired with other relevant data. This makes the table manageable and query-friendly.
Alternatively, the table can be normalized into multiple related tables. For instance, customer information and orders might be split into two tables, with a customer ID linking them. This ensures both tables are in 1NF while reducing redundancy.
The minimal acceptable normal form for any relation is 1NF. A table that satisfies 1NF is free from non-atomic values and repeating groups, forming the foundation for further normalization (e.g., 2NF, 3NF).
These methods ensure a consistent and structured database design, improving data integrity, scalability, and maintainability.