title: Relational Data Modeling Vocabulary
description: Core terms and concepts used in relational database design and data modeling.
version: 1.0.0
modified: '2026-05-02'
terms:
  - term: Relation
    definition: >-
      A mathematical set of tuples with named attributes. In relational databases,
      a relation is represented as a table with rows and columns.

  - term: Entity
    definition: >-
      A real-world object or concept that is represented as a table (relation) in a
      relational data model.

  - term: Attribute
    definition: >-
      A property or characteristic of an entity, represented as a column in a
      relational table.

  - term: Primary Key
    definition: >-
      A column or set of columns whose values uniquely identify each row in a table.
      A primary key cannot contain NULL values and must be unique.

  - term: Foreign Key
    definition: >-
      A column or set of columns in one table that references the primary key of another
      table, establishing a relationship between the two tables.

  - term: Entity-Relationship Diagram (ERD)
    definition: >-
      A visual representation of entities, their attributes, and the relationships between
      entities in a data model.

  - term: Normalization
    definition: >-
      The process of organizing a relational database to reduce data redundancy and
      improve data integrity by applying a series of normal forms.

  - term: First Normal Form (1NF)
    definition: >-
      A relation is in 1NF if every attribute contains only atomic (indivisible) values
      and each row is unique.

  - term: Second Normal Form (2NF)
    definition: >-
      A relation is in 2NF if it is in 1NF and every non-key attribute is fully
      functionally dependent on the entire primary key.

  - term: Third Normal Form (3NF)
    definition: >-
      A relation is in 3NF if it is in 2NF and no non-key attribute is transitively
      dependent on the primary key.

  - term: Boyce-Codd Normal Form (BCNF)
    definition: >-
      A stronger version of 3NF where every determinant is a candidate key, eliminating
      anomalies that 3NF does not address.

  - term: Candidate Key
    definition: >-
      A minimal set of attributes that uniquely identifies each tuple in a relation.
      A table may have multiple candidate keys.

  - term: Surrogate Key
    definition: >-
      An artificial, system-generated key (e.g., auto-incrementing integer) used as the
      primary key when no natural key is suitable.

  - term: Natural Key
    definition: >-
      A key formed from real-world attributes that inherently identify a record, such as
      a social security number or email address.

  - term: Functional Dependency
    definition: >-
      A constraint between two sets of attributes in a relation where the value of one
      attribute (or set) determines the value of another.

  - term: Join
    definition: >-
      A SQL operation that combines rows from two or more tables based on related columns,
      typically through foreign key relationships.

  - term: Referential Integrity
    definition: >-
      A database constraint ensuring that foreign key values always refer to existing
      primary key values in the referenced table.

  - term: DDL (Data Definition Language)
    definition: >-
      SQL statements used to define and modify database structures, including CREATE TABLE,
      ALTER TABLE, DROP TABLE, and CREATE INDEX.

  - term: Cardinality
    definition: >-
      The description of the numerical relationship between entities: one-to-one (1:1),
      one-to-many (1:N), or many-to-many (M:N).

  - term: Schema
    definition: >-
      The logical container in a database that organizes and groups related tables, views,
      and other database objects.