Entity-relationship diagrams (ERD) are essential to modeling anything from simple to complex databases, but the shapes and notations used can be very confusing. This guide will help you to become an expert in ER diagram notation, and you will be …

2023年12月21日 · An Entity Relationship Diagram (ERD) is a type of diagram that lets you see how different entities (e.g. people, customers, or other objects) relate to each other in an application or a database. They are created when a new system is being designed so that the development team can understand how to structure the database.

2021年8月1日 · Overview of different types of keys used in E-R diagrams. How to establish a primary key from a set of alternatives. Composite, superkey, candidate, primary and alternate keys explained. Other keys you may come across include foreign and partial keys.

2025年3月11日 · An Entity Relationship Diagram (ERD) is a graphical representation that shows how entities, such as people, objects, or concepts, relate to each other within a system. ERDs are commonly used in database design to visualize the relationships between entities …

实体关系图也被称为 ERD、ER 图、实体联系模型、实体联系模式图或 ER 模型，是一种用于数据库设计的结构图。 一幅 ERD 包含不同的符号和连接符，用于显示两个重要的資訊： 系统范围内的 主要实体，以及这些 实体之间的相互关系。 这也就是为什么它被称为“实体”“关系”图 （ERD）啊！ 当我们谈论 ERD 中的实体时，我们经常提到诸如人员/角色（例如学生），有形商业对象（例如产品），无形商业对象（例如日志）等业务对象。 “关系”則是这些实体在系统内的相互关联。 …

ER diagrams can be used for various purposes, ranging from abstract logical models devoid of any implementation details, through to physical models of relational database tables. It can be useful to include attribute definitions on ER diagrams to aid comprehension of the purpose and meaning of entities.

ERD stands for entity relationship diagram. People also call these types of diagrams ER diagrams and Entity Relationship Models. An ERD visualizes the relationships between entities like people, things, or concepts in a database.

An entity-relationship diagram, or ER diagram, models the logical relationships between entities and thereby can help engineers troubleshoot issues or discover inefficiencies in existing database designs. These diagrams can also help engineers design new databases and make sure they can uncover design flaws before they're implemented in production.

本文介绍了实体关系模型（ER Diagram）中超级键（Superkey）、键（Key）、候选键（Candidate Key）和复合键（Composite Key）的概念，并通过学生选课实例展示了如何建立E-R图，强调了主键（Primary Key）的选择过程。

Physical ERD symbols. The symbols below are used at the most granular level of ERDs—physical data models. Some elements are also used for logical data models. Tables are another way of representing entities. Fields represent attributes of the entity. Keys are one way to categorize attributes.