First Normal Form (1NF) in DBMS Theory - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding the core rule of 1NF

Which of the following best describes the main requirement of First Normal Form (1NF) in database design?

A All columns must contain only numeric data types.

B Each column must contain atomic, indivisible values with no repeating groups.

C Each table must have a foreign key referencing another table.

D Tables must be split into multiple databases.

💡 Hint

Think about how data is stored in each cell of a table.

1NF requires that each column holds atomic values, meaning no lists or sets inside a single cell, and no repeating groups of columns.

🚀 Application

intermediate

Identifying violation of 1NF

Given a table where a column 'PhoneNumbers' contains multiple phone numbers separated by commas in a single cell, what is the issue related to 1NF?

A The column violates 1NF because it contains multiple values in one cell.

B The column is correctly designed as it stores all phone numbers together.

C The table violates 1NF because it lacks a primary key.

D There is no violation; 1NF allows multiple values in one cell.

💡 Hint

Recall what atomic values mean in 1NF.

1NF requires each cell to hold only one value. Multiple phone numbers in one cell break this rule.

🔍 Analysis

advanced

Analyzing a table for 1NF compliance

Consider a table with columns: StudentID, Name, and Courses. The 'Courses' column contains a list of course names separated by semicolons. What is the correct way to bring this table into 1NF?

A Split the 'Courses' column so each course is in a separate row linked to the same StudentID.

B Keep the 'Courses' column as is because it shows all courses a student takes.

C Combine 'StudentID' and 'Courses' into one column to avoid lists.

D Remove the 'Courses' column entirely to comply with 1NF.

💡 Hint

Think about how to make each cell atomic without losing information.

To comply with 1NF, each cell must hold a single value. Splitting courses into separate rows keeps data atomic and preserves relationships.

❓ Comparison

advanced

Comparing 1NF with other normal forms

Which statement correctly distinguishes First Normal Form (1NF) from Second Normal Form (2NF)?

A 1NF requires tables to be split into multiple databases; 2NF requires atomic columns.

B 1NF requires no duplicate rows; 2NF requires atomic columns.

C 1NF requires foreign keys; 2NF requires unique keys.

D 1NF requires atomic columns; 2NF requires that all non-key columns depend fully on the primary key.

💡 Hint

Focus on the difference in dependency and atomicity rules.

1NF focuses on atomicity of data, while 2NF focuses on removing partial dependencies on a composite primary key.

❓ Reasoning

expert

Evaluating 1NF compliance in a complex scenario

A table stores customer orders with columns: OrderID, CustomerName, and ItemsOrdered. The 'ItemsOrdered' column contains JSON strings listing multiple items and quantities. Does this table comply with 1NF?

A Yes, because JSON is a single string and counts as atomic data.

B Yes, because 1NF allows complex data types like JSON in columns.

C No, because storing JSON strings means the column contains multiple values, violating atomicity.

D No, because the table lacks a composite primary key.

💡 Hint

Consider what atomic means beyond just data type.

Even if JSON is stored as a string, it represents multiple values inside one cell, violating 1NF's atomicity rule.