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When to Use the ER Diagram Generator
- During database design — visualize the schema before writing SQL
- Code reviews — share a diagram to explain schema changes
- Onboarding — help new developers understand the data model quickly
- Documentation — generate up-to-date diagrams from the actual DDL
- Migration planning — visualize the current and target schemas side by side
- Stakeholder communication — explain the data model to non-technical team members
The ER Diagram Generator on TechConverter.me turns SQL DDL into professional diagrams instantly, making database documentation and design communication effortless.
Examples
Example 1: Generating a Diagram from SQL DDL
Paste these CREATE TABLE statements into the generator:
CREATE TABLE users (
id SERIAL PRIMARY KEY,
email VARCHAR(255) UNIQUE NOT NULL,
name VARCHAR(100) NOT NULL,
created_at TIMESTAMP DEFAULT NOW()
);
CREATE TABLE products (
id SERIAL PRIMARY KEY,
name VARCHAR(200) NOT NULL,
price DECIMAL(10,2) NOT NULL,
stock INTEGER DEFAULT 0,
category_id INTEGER REFERENCES categories(id)
);
CREATE TABLE categories (
id SERIAL PRIMARY KEY,
name VARCHAR(100) NOT NULL,
slug VARCHAR(100) UNIQUE NOT NULL
);
CREATE TABLE orders (
id SERIAL PRIMARY KEY,
user_id INTEGER NOT NULL REFERENCES users(id),
total DECIMAL(10,2) NOT NULL,
status VARCHAR(20) DEFAULT 'pending',
created_at TIMESTAMP DEFAULT NOW()
);
CREATE TABLE order_items (
id SERIAL PRIMARY KEY,
order_id INTEGER NOT NULL REFERENCES orders(id) ON DELETE CASCADE,
product_id INTEGER NOT NULL REFERENCES products(id),
quantity INTEGER NOT NULL,
unit_price DECIMAL(10,2) NOT NULL
);
The generator produces a diagram showing:
- users → orders: one-to-many (one user has many orders)
- orders → order_items: one-to-many (one order has many items)
- products → order_items: one-to-many (one product appears in many order items)
- categories → products: one-to-many (one category has many products)
Example 2: Crow's Foot Notation
In crow's foot notation, relationship cardinality is shown with symbols at the ends of relationship lines:
users ||--o{ orders : "places"
(one user places zero or many orders)
orders ||--|{ order_items : "contains"
(one order contains one or many items)
products ||--o{ order_items : "included in"
(one product is included in zero or many order items)
categories ||--o{ products : "has"
(one category has zero or many products)
Crow's foot symbols:
||— exactly one (mandatory)|o— zero or one (optional)}|— one or many (mandatory many)}o— zero or many (optional many)
Example 3: Blog Database Schema
A blog application schema with users, posts, comments, and tags:
CREATE TABLE authors (
id SERIAL PRIMARY KEY,
username VARCHAR(50) UNIQUE NOT NULL,
email VARCHAR(255) UNIQUE NOT NULL,
bio TEXT
);
CREATE TABLE posts (
id SERIAL PRIMARY KEY,
author_id INTEGER NOT NULL REFERENCES authors(id),
title VARCHAR(300) NOT NULL,
slug VARCHAR(300) UNIQUE NOT NULL,
content TEXT NOT NULL,
published_at TIMESTAMP,
status VARCHAR(20) DEFAULT 'draft'
);
CREATE TABLE comments (
id SERIAL PRIMARY KEY,
post_id INTEGER NOT NULL REFERENCES posts(id) ON DELETE CASCADE,
author_id INTEGER REFERENCES authors(id),
content TEXT NOT NULL,
created_at TIMESTAMP DEFAULT NOW()
);
CREATE TABLE tags (
id SERIAL PRIMARY KEY,
name VARCHAR(50) UNIQUE NOT NULL
);
CREATE TABLE post_tags (
post_id INTEGER NOT NULL REFERENCES posts(id) ON DELETE CASCADE,
tag_id INTEGER NOT NULL REFERENCES tags(id) ON DELETE CASCADE,
PRIMARY KEY (post_id, tag_id)
);
The generator identifies the many-to-many relationship between posts and tags through the post_tags junction table and renders it correctly in the diagram.