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Relational Data Model Overview

Jun 11, 2025

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Overview

This lecture introduces the relational data model, its history, key concepts, and basic terminology essential to understanding relational database management systems (RDBMS).

History of Relational Data Model

  • The relational data model was introduced in 1970 by Edgar F. Codd, a computer scientist at IBM.
  • It organizes data in tables with rows and columns, simplifying data storage and retrieval.
  • The model is based on mathematical relations and set theory.
  • First commercial implementations were by Oracle and IBM (SQL/DS).
  • Popular RDBMS today include SQL Server, Access, DB2, and Informix.
  • SQL became the standard query language for RDBMS.

Basic Relational Model Concepts

  • Relational model represents data as collections of tables (relations).
  • A table in RDBMS is also called a relation.
  • Each row in a table is known as a tuple.
  • Each column or header is called an attribute or field.

Important Terminology

  • Domain: Set of possible atomic values allowed for an attribute (e.g., ages 20–70 for employee age).
  • Relation Schema: Describes a relation; consists of a name and list of attributes (with their data types).
  • Degree (Arity): Number of attributes in a relation schema (e.g., 6 attributes means degree is 6).
  • Cardinality: Number of tuples (rows) in a relation (e.g., 3 tuples means cardinality is 3).
  • Relational Database Schema: Set of relation schemas and their integrity constraints for an entire database.
  • Relation State (Instance): Set of tuples in a relation at a specific point in time.

Key Terms & Definitions

  • Relation — A table consisting of rows (tuples) and columns (attributes).
  • Tuple — A single row in a relation (table).
  • Attribute — A single column in a relation, also called a field.
  • Domain — Allowed set of atomic values for an attribute.
  • Relation Schema — Structure defining a relation’s name and its attributes.
  • Degree (Arity) — Number of attributes in a relation.
  • Cardinality — Number of tuples (rows) in a relation.
  • Relational Database Schema — Set of all relation schemas and integrity constraints in a database.
  • Relation State (Instance) — Collection of tuples in a relation at a specified time.

Action Items / Next Steps

  • Review lecture notes on relational model terminology.
  • Prepare for upcoming material on SQL query language.

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