Key Concepts in Relational Databases

Attribute

A characteristic or property of an entity, represented as a column in a database table.

Cardinality

Indicates the number of instances of one entity that can be associated with the number of instances of another entity in a relationship (e.g., one-to-one, one-to-many, many-to-many).

Candidate Key

A minimal set of attributes that can uniquely identify a record in a table. This key can be chosen as the primary key.

Composite Key

A combination of two or more columns used as a primary key. It is used when a single column is not sufficient to uniquely identify a record

Data Integrity

The accuracy, consistency, and reliability of data stored in a database.

Database Management System (DBMS)

Software that manages and provides access to a database.

Entity

A real-world object or concept that is represented in a database.

Entity Relationship Diagram (ERD)

A visual representation of entities and their relationships within a database.

Foreign Key

An attribute in a table that refers to the primary key of another table, establishing a relationship between them.

Functional Dependency

A relationship where the value of one attribute determines the value of another attribute.

Multivalued Attribute

An attribute that can hold multiple values for a single entity instance.

Normalization

A process of organizing data in a database to reduce data redundancy and improve data integrity.

Primary Key

An attribute or a set of attributes that uniquely identifies a record in a table.

Referential Integrity

A constraint that ensures all foreign key values reference valid primary keys in related tables.

Relation

A table with rows (tuples) and columns (attributes) representing data in a relational database.

Relational Database

A type of database that stores data in tables with relationships defined between them.

Surrogate Key

A system-generated, artificial key used as a primary key instead of a natural key.

Supertype/Subtype

A hierarchical relationship where a supertype represents a general entity type and subtypes represent specialized categories within that entity type.

Weak Entity

An entity that cannot exist without a corresponding entity, typically identified by a partial key.