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Database Schema

A structure that defines the organization of data in a database, specifying tables, fields, data types, and relationships.

Tuple

A tuple is a row in a table representing a single record in a relational database.

Attribute

An attribute refers to a column in a table, representing a specific piece of information about each tuple.

Domain

The set of allowed values for each attribute in a database relation.

Primary Key

An attribute or a set of attributes that uniquely identifies each tuple in a relation.

Foreign Key

An attribute in a table that links to the primary key of another table, establishing a relationship between the two tables.

Relational Model

A data model based on first-order predicate logic, where data is represented in tables (relations).

Relational Algebra

A formal system for manipulating relations, consisting of operations like selection, projection, and join.

Selection Predicate

A condition applied to tuples in order to retrieve a subset of data from a relation.

Natural Join

A join operation that combines two relations by matching tuples with identical values in their common attributes.

Set Difference

An operation that finds the difference between two sets, returning tuples that are present in the first set but not in the second.

Union

An operation that combines the tuples of two relations, eliminating duplicates.

Projection

An operation that retrieves specific attributes (columns) from a relation.

Cartesian Product

An operation that returns all possible pairs of tuples from two relations.

Candidate Key

A minimal superkey; an attribute or a set of attributes that can uniquely identify a tuple.

Entity-Relationship Model

A conceptual framework used to describe the structure of data and its relationships, primarily for database design.