CS-GY 6083: Principles of Database Systems
1.0.0
1.0.0
  • Introduction
  • DBMS Basics
    • Introduction to DBMS
    • Why use a DBMS instead of a File System?
    • Levels of Abstraction
    • Instances and Schemas
  • Data Models
    • Introduction to Data Models
    • Database Languages
    • Database Design
  • DBMS Internals
    • Introduction to DBMS Internals
    • Storage Manager
    • Query Processor
    • Transaction Management
    • Database Users
    • Database Architecture
  • DBMS History
  • Some Popular Database Systems
  • OLTP, OLAP, and Data Mining
  • Databases vs. Information Retrieval
  • The Entity-Relationship Model - Details
    • Introduction
    • Cardinality Constraints
    • ER Diagram Components
    • ER Diagram to Relational Schema
    • Design Issues
  • The Relational Model - Details
    • Relations
    • Keys
    • Relational Query Languages
      • Relational Algebra
      • Relational Calculus
      • Relative Expressive Power
    • Relational Operators
  • SQL
    • Introduction to SQL
    • Domain Types in SQL
    • DDL Commands
      • Creating a Table
      • Alter and Drop
    • DML Commands
      • Basic Query Structure
      • Select
      • From
      • Where
      • Joins
      • Rename
      • String Operations
      • Ordering
      • Set Operations
      • Group By and Having
      • Nested Subqueries
      • Test for Empty Relations
      • Test for Duplicate Tuples
      • Derived Relations
      • With
      • Database Modification
    • Intermediate SQL
      • Joins Revisited
      • Views
      • Transactions
      • Integrity Constraints
      • More SQL Data Types and Schemas
        • Other Features
      • Authorization
    • Advanced SQL
      • Accessing SQL From a Programming Language
        • ODBC and JDBC
        • Embedded SQL
        • PHP
        • Some Security Issues
      • Accessing Metadata
      • Text Operations
        • Like
        • Contains
      • Cursors
      • Functions and Procedures
        • Procedural Constructs
        • External Language Routines
      • Triggers
      • Ranking
      • Windowing
      • OLAP
Powered by GitBook
On this page

Was this helpful?

  1. The Entity-Relationship Model - Details

Cardinality Constraints

They help us express the number of entities to which another entity can be associated via a relationship set.

They are most helpful in binary relationship sets.

For a binary relationship set, the mapping cardinality must be one of the following types:

  • one to one

  • one to many

  • many to one

  • many to many

In a ternary relationship, we usually limit the number of one-one relationships (denoted by an arrow) to 1.

If there is more than one arrow, there are two ways of defining the meaning:

A ternary relationship R between A, B and C with arrows to B and C could mean:

  1. Each A entity is associated with a unique entity from B and C (or)

  2. Each pair of entities from (A, B) is associated with a unique C entity, and each pair (A, C) is associated with a unique B

PreviousIntroductionNextER Diagram Components

Last updated 5 years ago

Was this helpful?