What are the different normal forms (1NF, 2NF, 3NF, BCNF, 4NF, etc.)?

Normal forms are guidelines used to organize a relational database schema. Each form

addresses a different kind of redundancy or dependency.

• 1NF (First Normal Form):
• A table is in 1NF if it contains only atomic (indivisible) values and each record

has a unique identifier (Primary Key).

• No repeating groups or arrays are allowed.
• 2NF (Second Normal Form):
• A table is in 2NF if it is in 1NF and all non-key attributes are fully

functionally dependent on the primary key.

• Eliminates partial dependency (when a non-key attribute depends on only

part of a composite primary key).

• 3NF (Third Normal Form):
• A table is in 3NF if it is in 2NF and there are no transitive dependencies

(non-key attributes depending on other non-key attributes).

• This removes dependencies between non-key attributes.
• BCNF (Boyce-Codd Normal Form):
• A table is in BCNF if it is in 3NF and every determinant is a candidate key.
• This is a stricter version of 3NF.
• 4NF (Fourth Normal Form):
• A table is in 4NF if it is in BCNF and multi-valued dependencies are

removed.

• This ensures that a record doesn’t have two or more independent

multi-valued attributes.

• 5NF (Fifth Normal Form):
• A table is in 5NF if it is in 4NF and cannot be decomposed further without

losing data.