Database Systems Final - Normalization

What is a primary key

An attribute that uniquely identifies rows; cannot be null

What is a foreign key

An attribute that references a primary key in another table

What is entity integrity

Primary key attributes cannot be null

What is referential integreity

Foreign key must match a primary key or be null

What is a domain constraint

Rules defining allowable attribute values

Definition of functional dependency

A determines B if each value of A uniquely determines a value of B

What is a relation in 1NF

When it has no multivalued attributes and all values are atomic

When is a relation in 2NF

No partial dependencies (non-key depends on part of composite key)

When is a relation in 3NF

No transitive dependencies (non-key depends on non-key)

What is non loss decomposition

When decomposed tables can be joined to restore the original relation

What determines record size

Total storage size of all attributes in a table row

What is denormalization

Reintroducing redundancy to improve performance (3NF → 2NF)

When is denormalization used

When a normalized structure causes slow joins or heavy querying

What is horizontal partitioning

Splitting a table by rows

What is vertical partitioning

Splitting a table by columns

What is an index

A data structure that speeds up searching and retrieval

What is the tradeoff of indexes

Faster reads but slower writes (updates/ inserts)