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Yoshiki Kajihara edited this page Oct 18, 2025 · 1 revision

ERD Designer User Manual

Note

This manual is currently under development and may contain errors or incomplete information.

Manual Table of Contents

1. Introduction

1.1 What is ERD Designer?

ERD Designer (Entity Relationship Diagram Designer) is a web-based tool for designing database entity relationship diagrams (ER diagrams). With this tool, you can intuitively design database table structures and relationships between tables through a graphical interface.

This tool is inspired by ERMaster, which was widely used as an ER modeling tool for Eclipse. ERD Designer has evolved to be more user-friendly by leveraging modern web technologies. Its primary purpose is to enable efficient and accurate database design in the early stages of application development projects.

1.2 Key Features and Benefits

Graphical Design Environment

ERD Designer allows you to place tables with mouse operations and create relationships using drag-and-drop. This makes it easy to visually understand complex database structures during the design process.

Support for Various Output Formats

ER diagrams you design can be exported in the following formats:

  • PNG Image Files: Save ER diagrams as images for use in documents and presentations.
  • DDL (Data Definition Language) Files: Automatically generate CREATE TABLE statements for your selected database. You can choose necessary elements such as table definitions, indexes, foreign key constraints, comments, and schemas for output.
  • Table Specification Documents: Export design content for use in specification documentation. For online tools, output to Excel files; for Google Drive App, output to Google Spreadsheet in the home directory.
  • ERD Files (.erd): Save design data as files for backup or migration to other environments.

DDL Import Feature (Experimental)

You can import DDL generated from existing databases to automatically create ER diagrams. It supports DDL from PostgreSQL, MySQL, and MS SQL Server, and can be used for reverse engineering and database visualization.

Note

The DDL import feature is experimental. It may not support complex DDL syntax or some advanced features.

Schema Management Feature

ERD Designer supports management of schemas used in PostgreSQL and MS SQL Server. You can assign schemas to each table, and appropriate schema names will be included when exporting DDL.

Column Model Reuse Feature

Column definitions are automatically registered as column models and can be reused across multiple tables. This maintains design consistency while improving work efficiency.

Local Storage (Online Tool Only)

Data for ER diagrams you create is entirely stored in the browser's local storage. Data is never sent to online servers, so you can use it with confidence even for confidential projects.

Important

Because data is saved in the browser's local storage, ER diagram data created in one browser is not shared between different browsers or different machines. However, you can export an erd file from the source and import it into another browser to transfer data between browsers or machines.

Caution

Because data is saved in the browser's local storage, clearing the browser's cache will delete the ER diagram data you created. Please be careful when performing cache clearing operations.

Tip

When using the Google Drive App mode described below, only pre-specified files on Google Drive are updated. ER diagram data you create is never sent to external servers other than Google Drive.

1.3 Tool Usage Modes and Prerequisites

Available Modes

ERD Designer offers two usage modes depending on your needs and environment:

  1. Online Tool: Access kajitiluna.github.io/erd-designer to start using it immediately in your browser. No installation is required, making it the easiest way to get started.

    • Data is saved in the browser's IndexedDB
    • Table specification documents are exported as Excel files

  2. Google Drive App: Install from ERD Designer - Google Workspace Marketplace to save and manage .erd files containing ERD Designer work on Google Drive.

    • File management on Google Drive is possible
    • Table specification documents are exported as Google Spreadsheets
    • Team sharing and backup become easier

Important

In Google Drive App mode, multiple users cannot edit the same file simultaneously.

Prerequisites and Target Users

  • Technical Prerequisites:
    • Modern web browser (Chrome, Firefox, etc.)
    • JavaScript enabled
    • IndexedDB support (for online tool)
    • Google Drive access permissions (for Google Drive App)
  • Knowledge Prerequisites: Targeted at software engineers with basic knowledge of database design (tables, columns, primary keys, foreign keys, normalization, relationships, etc.).
  • Usage Scenarios: Intended for use during the database design phase of new application development.

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