{"id":414,"date":"2025-03-10T16:07:04","date_gmt":"2025-03-10T20:07:04","guid":{"rendered":"https:\/\/sites.nd.edu\/businessanalysis\/?page_id=414"},"modified":"2025-03-10T17:15:00","modified_gmt":"2025-03-10T21:15:00","slug":"entity-relationship-diagram-erd","status":"publish","type":"page","link":"https:\/\/sites.nd.edu\/businessanalysis\/?page_id=414","title":{"rendered":"Entity-Relationship Diagram (ERD)"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\"><strong>1. What is an Entity-Relationship Diagram?<\/strong><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>An Entity-Relationship Diagram (ERD) is a visual representation of the data structure of a system. It shows the relationships between data entities in a database. <\/li>\n\n\n\n<li>ERDs are widely used in database design to model the relationships between data elements and ensure a well-structured database schema.<\/li>\n\n\n\n<li><strong>Key Benefits:<\/strong>\n<ul class=\"wp-block-list\">\n<li>Helps in database design by organizing data efficiently.<\/li>\n\n\n\n<li>Clarifies business rules and relationships between data elements.<\/li>\n\n\n\n<li>Improves communication between database developers, business analysts, and stakeholders.<\/li>\n\n\n\n<li>Reduces data redundancy and ensures data integrity in relational databases.<\/li>\n\n\n\n<li>ERDs are essential in database normalization, ensuring a well-structured and scalable database model.<\/li>\n\n\n\n<li>Helpful in depicting system architecture.<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>2. Common Diagramming Symbols<\/strong><\/h2>\n\n\n\n<table id=\"tablepress-5\" class=\"tablepress tablepress-id-5\">\n<thead>\n<tr class=\"row-1\">\n\t<th class=\"column-1\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/sites.nd.edu\/businessanalysis\/files\/2025\/02\/ProcessStep.jpg\" alt=\"\" width=\"85\" height=\"43\" class=\"alignnone size-full wp-image-84\" \/><\/th><th class=\"column-2\">Entities: Rectangles represent objects or concepts that store data.<\/th>\n<\/tr>\n<\/thead>\n<tbody class=\"row-hover\">\n<tr class=\"row-2\">\n\t<td class=\"column-1\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/sites.nd.edu\/businessanalysis\/files\/2025\/03\/Oval-1.jpg\" alt=\"\" width=\"91\" height=\"58\" class=\"alignnone size-full wp-image-422\" \/><\/td><td class=\"column-2\">Attributes: Ellipses (ovals) connected to a rectangle describe properties or characteristics of an entity.<\/td>\n<\/tr>\n<tr class=\"row-3\">\n\t<td class=\"column-1\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/sites.nd.edu\/businessanalysis\/files\/2025\/03\/Relationships-1.jpg\" alt=\"\" width=\"188\" height=\"66\" class=\"alignnone size-full wp-image-423\" \/><\/td><td class=\"column-2\">Relationships: Diamonds or labeled lines define the associations between entities.<\/td>\n<\/tr>\n<tr class=\"row-4\">\n\t<td class=\"column-1\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/sites.nd.edu\/businessanalysis\/files\/2025\/03\/Primary-Key-1.jpg\" alt=\"\" width=\"182\" height=\"61\" class=\"alignnone size-full wp-image-424\" \/><\/td><td class=\"column-2\">Primary Key (PK): Attributes that are underlined and\/or marked with \"PK\" indicate a unique identifier for each record in an entity.<\/td>\n<\/tr>\n<tr class=\"row-5\">\n\t<td class=\"column-1\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/sites.nd.edu\/businessanalysis\/files\/2025\/03\/Foreign-Key-1.jpg\" alt=\"\" width=\"181\" height=\"58\" class=\"alignnone size-full wp-image-425\" \/><\/td><td class=\"column-2\">Foreign Key (FK): A dashed underline or italicized text denotes an attribute that establishes a relationship between two entities by referencing a primary key from another entity.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<!-- #tablepress-5 from cache -->\n\n\n\n<ul class=\"wp-block-list\">\n<li>The symbols used are typically based on the tool notation (e.g., Chen &amp; SQL, Crow\u2019s Foot, UML).<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>3. Relationship Types<\/strong><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Entities can have a variety of relationship types with other entities.<\/li>\n\n\n\n<li>The three most common are:\n<ul class=\"wp-block-list\">\n<li>One-to-One (1:1): Each entity instance relates to only one instance of another entity.<\/li>\n\n\n\n<li>One-to-Many (1:M): One entity instance relates to multiple instances of another entity.<\/li>\n\n\n\n<li>Many-to-Many (M:N): Multiple instances of one entity relate to multiple instances of another entity.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>Symbols can also be used to denote relationships. Below are some examples of relationship symbols:<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-image size-full is-resized\"><img loading=\"lazy\" decoding=\"async\" width=\"416\" height=\"149\" src=\"https:\/\/sites.nd.edu\/businessanalysis\/files\/2025\/03\/Relationship-Notation.jpg\" alt=\"\" class=\"wp-image-429\" style=\"width:367px;height:auto\" srcset=\"https:\/\/sites.nd.edu\/businessanalysis\/files\/2025\/03\/Relationship-Notation.jpg 416w, https:\/\/sites.nd.edu\/businessanalysis\/files\/2025\/03\/Relationship-Notation-300x107.jpg 300w\" sizes=\"auto, (max-width: 416px) 100vw, 416px\" \/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>3. Example<\/strong>s<\/h2>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"782\" height=\"378\" src=\"https:\/\/sites.nd.edu\/businessanalysis\/files\/2025\/03\/ERD-Examples.jpg\" alt=\"\" class=\"wp-image-445\" srcset=\"https:\/\/sites.nd.edu\/businessanalysis\/files\/2025\/03\/ERD-Examples.jpg 782w, https:\/\/sites.nd.edu\/businessanalysis\/files\/2025\/03\/ERD-Examples-300x145.jpg 300w, https:\/\/sites.nd.edu\/businessanalysis\/files\/2025\/03\/ERD-Examples-768x371.jpg 768w\" sizes=\"auto, (max-width: 782px) 100vw, 782px\" \/><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>1. What is an Entity-Relationship Diagram? 2. Common Diagramming Symbols 3. Relationship Types 3. Examples<\/p>\n","protected":false},"author":4975,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-414","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/sites.nd.edu\/businessanalysis\/index.php?rest_route=\/wp\/v2\/pages\/414","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sites.nd.edu\/businessanalysis\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/sites.nd.edu\/businessanalysis\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/sites.nd.edu\/businessanalysis\/index.php?rest_route=\/wp\/v2\/users\/4975"}],"replies":[{"embeddable":true,"href":"https:\/\/sites.nd.edu\/businessanalysis\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=414"}],"version-history":[{"count":8,"href":"https:\/\/sites.nd.edu\/businessanalysis\/index.php?rest_route=\/wp\/v2\/pages\/414\/revisions"}],"predecessor-version":[{"id":446,"href":"https:\/\/sites.nd.edu\/businessanalysis\/index.php?rest_route=\/wp\/v2\/pages\/414\/revisions\/446"}],"wp:attachment":[{"href":"https:\/\/sites.nd.edu\/businessanalysis\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=414"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}