Database normalization is a way to organize relational tables so that facts are stored consistently and unnecessary repetition is reduced. This lesson introduces the purpose of normalization, the problems it addresses, and its benefits when a database changes.
Database normalization structures the columns (attributes) and tables (relations) of a relational database according to formal rules called normal forms. These rules help ensure that data dependencies are represented appropriately and enforced through database integrity constraints.
All flashcards
Database normalization
Structuring relational tables according to normal forms so dependencies are represented appropriately and unnecessary redundancy is reduced.
Insertion, update, and deletion anomalies
Side effects of poorly grouped or repeated facts that can make records difficult to add, change, or remove consistently.
Candidate key
A minimal key that uniquely identifies a row and could be selected as the primary key.
Functional dependency
A relationship in which one attribute or attribute set determines another attribute's value.
Sixth normal form (6NF)
An intuitive form in which a row contains a primary key and at most one other attribute.
Quiz questions
Which condition defines first normal form (1NF) in a relational table?Answer: Each field contains a single value, not a set or nested record.
For a relation with composite candidate key {A, B}, which dependency signals a 2NF violation?Answer: A non-key attribute is determined by A alone.
Which pattern describes a transitive dependency relevant to 3NF?Answer: A key determines a non-key attribute that determines another non-key attribute.
What does fifth normal form (5NF) assess about decomposing a relation?Answer: Whether projections can be joined to reconstruct the relation without spurious tuples or information loss.
What is the central aim of domain-key normal form (DKNF)?Answer: Constraints should follow from domain constraints and key constraints.