What is the difference between an ER diagram and a schema diagram?

An ER diagram models the conceptual design of a database — entities and their relationships. A schema diagram shows the physical implementation: actual table names, column types, primary/foreign keys. Both are often called ER diagrams colloquially.

Can it reverse-engineer diagrams from existing databases?

This tool works from SQL DDL (CREATE TABLE scripts). For live reverse-engineering from a running database, use tools like DBeaver, pgAdmin (PostgreSQL), or MySQL Workbench which connect directly and generate diagrams from the live schema.

What SQL dialects are supported?

PostgreSQL, MySQL, SQLite, and ANSI SQL syntax are parsed. Dialect-specific features (like MySQL AUTO_INCREMENT vs PostgreSQL SERIAL vs IDENTITY) are handled. SQL Server T-SQL and Oracle PL/SQL have limited support.

Database Schema Diagram | DevTools Surf

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Example: Database Schema Diagram

A worked example, rendered from real sample data. Sign in to run the tool on your own input.

Input

users
posts
comments

Output

{
  "diagram": "erDiagram\n    USERS ||--o{ POSTS : writes\n    USERS ||--o{ COMMENTS : makes\n    POSTS ||--o{ COMMENTS : receives\n    USERS ||--o{ LIKES : gives\n    POSTS ||--o{ LIKES : receives\n    USERS {\n        int id PK\n        string email UK \"unique\"\n        string username UK \"unique\"\n        string password_hash\n        datetime created_at\n        datetime updated_at\n    }\n    POSTS {\n        int id PK\n        int user_id FK\n        string title\n        text content\n        int view_count\n        datetime published_at\n    }\n    COMMENTS {\n        int id PK\n        int post_id FK\n        int user_id FK\n        text content\n        datetime created_at\n    }\n    LIKES {\n        int id PK\n        int post_id FK\n        int user_id FK\n        datetime created_at\n    }",
  "format": "mermaid",
  "title": "Database Schema (ER Diagram)",
  "tables": [
    "users",
    "posts",
    "comments",
    "likes"
  ],
  "relationships": [
    "users-posts",
    "users-comments",
    "users-likes",
    "posts-comments",
    "posts-likes"
  ]
}

About Database Schema Diagram

Database Schema Diagram preview - Diagrams & Workflows tool

Generate database schema diagrams with tables, relationships, and field definitions. Part of the DevTools Surf developer suite. Browse more tools in the Diagrams & Workflows collection.

Use Cases

Visualize an existing database schema for documentation or onboarding
Generate ER diagrams from SQL DDL for architecture reviews
Export schema diagrams for inclusion in technical design documents
Understand table relationships in an unfamiliar legacy codebase

Tips

Paste a CREATE TABLE SQL script — the generator extracts tables, columns, types, primary keys, and FOREIGN KEY constraints automatically
Use the relationship layout options: normalized (foreign keys as lines), crow's foot (ERD notation), or UML (class diagram style)
Export as PNG for documentation or as SQL DDL to reconstruct the schema from the diagram

Fun Facts

Entity-relationship (ER) diagrams were invented by Peter Chen in 1976. His original paper 'The Entity-Relationship Model: Toward a Unified View of Data' is one of the most cited papers in database research.
Crow's foot notation, the most common ER diagram notation in use today, was developed by Gordon Everest in 1976 (independently of Chen) and popularized by James Martin in the 1980s. The 'crows feet' symbol represents zero, one, or many cardinality.
The relational model of data was proposed by E.F. Codd at IBM in 1970 in his paper 'A Relational Model of Data for Large Shared Data Banks.' This paper created the theoretical foundation for SQL and all relational databases — one of the most influential computer science papers ever written.

FAQ

What is the difference between an ER diagram and a schema diagram?: An ER diagram models the conceptual design of a database — entities and their relationships. A schema diagram shows the physical implementation: actual table names, column types, primary/foreign keys. Both are often called ER diagrams colloquially.
Can it reverse-engineer diagrams from existing databases?: This tool works from SQL DDL (CREATE TABLE scripts). For live reverse-engineering from a running database, use tools like DBeaver, pgAdmin (PostgreSQL), or MySQL Workbench which connect directly and generate diagrams from the live schema.
What SQL dialects are supported?: PostgreSQL, MySQL, SQLite, and ANSI SQL syntax are parsed. Dialect-specific features (like MySQL AUTO_INCREMENT vs PostgreSQL SERIAL vs IDENTITY) are handled. SQL Server T-SQL and Oracle PL/SQL have limited support.

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