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Entity Management

Entities are the fundamental building blocks of an ERD, representing a collection of data managed by the business. In relational databases, they correspond to tables, and each entity has attributes (columns) and identifiers (PK).

Creating Entities

Two ways to add entities to the canvas:

Method Action
Toolbar Click the Add Entity icon in the top toolbar
Context Menu Right-click on an empty canvas area → Add Entity

Created entities are placed on the canvas with a default name (NewEntity). Drag them to your desired position.

Editing Entities

Double-click an entity or right-click → Edit to open the edit dialog.

Edit Entity Dialog — logical/physical name input, column list, and settings

Basic Properties

Property Description Use Case
Logical Name Business-friendly name (shown in logical mode) Business communication, stakeholder review
Physical Name Table name (shown in physical mode) DDL generation, developer handoff
Description Descriptive memo for the entity Data dictionary, team sharing

Naming Conventions

  • Logical Name: Use business terminology (e.g., Customer, Order, Product)
  • Physical Name: Use standardized abbreviations (e.g., CUSTOMER, ORD, PROD)
  • Physical names typically use UPPERCASE + UNDERSCORE (_) format
  • If standard words are registered, physical names are auto-generated from logical name input

Style Customization

Customize the visual properties of entities for domain differentiation or importance highlighting:

  • Background color — Domain-specific color coding (e.g., order domain in blue, member domain in green)
  • Border color — Highlight critical entities
  • Resize — Drag entity corners to resize

Select an entity to display the Property Bar in the toolbar for instant color and style changes.

Entity Canvas Layout — entities with domain-specific colors and relationships

Column Management

Adding Columns

Click the + Add button in the column list of the edit dialog, or press Tab in the last column to add a new column.

Column Properties

Property Description Barker's Notation
PK Primary Key — unique identifier for the entity Shown by UID Bar (left vertical bar)
FK Foreign Key — automatically set when creating relationships Visualized by relationship lines
Logical Name Business attribute name Shown in logical mode
Physical Name Column name Shown in physical mode
Data Type VARCHAR, INTEGER, DECIMAL, DATE, etc. —
NOT NULL Required field Expressed by optionality marker
UNIQUE Uniqueness constraint —

Data Type Selection Guide

Data Nature Recommended Type Example
Short text (names, codes) VARCHAR(n) Customer name, product code
Integer (quantities, sequences) INTEGER Order quantity, sort order
Currency, decimals DECIMAL(p,s) Order amount, exchange rate
Date DATE Order date, birth date
Date + time TIMESTAMP Created at, modified at
Long text TEXT / CLOB Remarks, detailed description
Boolean (yes/no) BOOLEAN Active flag, deleted flag

Using Domains

Instead of manually specifying data types each time, define Standard Domains to automatically apply consistent types to columns of the same nature.

Reordering Columns

Reorder columns via drag and drop. By convention, PK columns are always positioned at the top.

Practical Example: E-Commerce ERD Design

Walk through the process of designing core entities for a simple e-commerce system.

Step 1: Identify Core Entities

Identify the data to be managed from business requirements:

Entity Logical Name Physical Name Description
Customer Customer CUSTOMER Service user
Product Product PRODUCT Product for sale
Order Order ORD Customer's purchase action
Order Item Order Item ORD_DTL Individual product within an order

Step 2: Define Columns

Define attributes for each entity:

PK Column Physical Name Type NOT NULL
✅ Customer No CUST_NO VARCHAR(20) ✅
Customer Name CUST_NM VARCHAR(100) ✅
Email EMAIL VARCHAR(200)
Phone TEL_NO VARCHAR(20)
Join Date JOIN_DT DATE ✅
PK Column Physical Name Type NOT NULL
✅ Product Code PROD_CD VARCHAR(20) ✅
Product Name PROD_NM VARCHAR(200) ✅
Unit Price UNIT_PRC DECIMAL(18,2) ✅
Category CTGR_CD VARCHAR(10)
PK Column Physical Name Type NOT NULL
✅ Order No ORD_NO VARCHAR(20) ✅
FK Customer No CUST_NO VARCHAR(20) ✅
Order Date ORD_DT DATE ✅
Order Amount ORD_AMT DECIMAL(18,2)

Step 3: Connect Relationships

  • Customer → Order: 1:N (one customer can have multiple orders)
  • Order → Order Item: 1:N (one order contains multiple items)
  • Product → Order Item: 1:N (one product can appear in multiple orders)

→ For relationship creation methods, see Relationships & FK.

Subtypes

Represent supertype–subtype relationships using Subtypes. For example, an Employee entity can be classified into Permanent, Contract, and Intern.

  1. Right-click on the entity → Define Subtype
  2. Configure in the subtype dialog:
Field Description
Discriminator Specify the Discriminator Column
Subtype Items Add sub-types (e.g., Permanent, Contract)
Discriminator Value Identification value for each item (e.g., PERM, CONT)
Inclusion Mode Inclusive / Exclusive mode

Subtypes are visualized as nested boxes within the entity node.

→ Subtype details: Subtypes

Notes & Zones

Auxiliary elements to enrich the canvas beyond entities.

Element Purpose Creation
Note Node Design notes, business rules, TODO memos Toolbar Add Note or right-click
Zone Node Visual grouping of related entities (domain boundaries) Toolbar Add Zone
  • Notes support rich-text editing (bold, italic, lists, etc.)
  • Placing entities inside Zones creates visual domain boundaries that greatly improve readability

→ Detailed guide: Notes & Zones