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SQL to ER Diagram

Parse CREATE TABLE statements and automatically generate ER diagrams in Mermaid format. Securely visualize your DB design entirely within the browser.

Guide: How to use & features

  • Enter or paste SQL `CREATE TABLE` statements into the text area.
  • Click the "Visualize" button to generate and display the ER diagram using Mermaid syntax.
  • Table relationships (Foreign Keys) are automatically extracted from `FOREIGN KEY` or `REFERENCES` clauses.
  • Use the "Copy Mermaid Code" button to save the generated syntax to your clipboard.
  • Your schema data is processed entirely in the browser, ensuring privacy and security.

Samples: Examples

Users and Posts (One-to-Many)

Input

CREATE TABLE users (
  id INT PRIMARY KEY,
  name VARCHAR(50)
);

CREATE TABLE posts (
  id INT PRIMARY KEY,
  user_id INT REFERENCES users(id),
  title VARCHAR(100)
);

Output

erDiagram
    users {
        INT id PK
        VARCHAR(50) name
    }
    posts {
        INT id PK
        INT user_id
        VARCHAR(100) title
    }

    posts }|--|| users : "user_id -> id"

FAQ: FAQ

  • Does it support all SQL dialects?

    It supports standard SQL CREATE TABLE syntax. Some highly specific proprietary vendor extensions may not be fully parsed as it uses a custom regex-based parser.

  • Is my data sent to a server?

    No. All processing is done locally in your browser via JavaScript. Your SQL code never leaves your computer.

  • What if relationships are not showing up?

    Ensure that your statements include FOREIGN KEY or REFERENCES clauses. The tool relies on these constraints to identify and draw relationships.

Use cases: Common Use Cases

  • Database Documentation

    Quickly visualize and document existing table structures by pasting SQL exports.

  • Schema Design Verification

    Self-check your DDL to ensure that relationships and constraints are correctly defined during the design phase.

  • Team Collaboration

    Share specific sub-system structures with your team using lightweight Mermaid syntax before generating full documentation.

Notes: Notes & Limitations

  • Limited SQL Syntax

    Statements other than CREATE TABLE (e.g., stored procedures, triggers, complex INDEX definitions) are ignored.

  • Performance with Large Schemas

    Very large schemas with dozens of tables may significantly impact browser rendering performance.

  • Syntax Errors

    Incomplete or malformed SQL statements (missing parentheses, typos) will result in parsing failures.
erDiagram USERS ||--o{ POSTS : "user_id -> id" USERS { int id PK string name } POSTS { int id PK int user_id string title }

About the SQL to ER Diagram (Mermaid) Generator

This online tool automatically generates Entity-Relationship (ER) diagrams in Mermaid.js format directly from your SQL DDL statements (CREATE TABLE).
Visualizing schemas directly from your database definitions dramatically improves efficiency during database design reviews and documentation creation.

How It Works & Privacy

This tool runs entirely in your browser using JavaScript. The SQL statements you input, including table structures and foreign key relationships, are never transmitted to any external servers.
You can safely use it to visualize the most sensitive internal database schemas without any risk of information exposure.

Articles for this tool

Introduction
2026-02-19

Generate ER Diagrams from SQL DDL: How CREATE TABLE Parsing Works

How the SQL to ER diagram tool parses CREATE TABLE DDL into a Mermaid ER diagram — the PRIMARY KEY/FOREIGN KEY extraction rules, how column types are handled, and which DDL patterns aren't supported.

Introduction
2026-08-03

How CREATE TABLE Generation From a Visual Table Design Works | DDL Builder

A look inside DDL Builder, which turns a visually designed table into CREATE TABLE statements and an ER diagram. Covers the MySQL/PostgreSQL/SQLite type-mapping rules and the column-inference algorithm used for JSON samples.

Use Case
2026-08-06

SQL Clause Order Reference: Why WHERE Can't See Your SELECT Alias

The order you write SQL clauses is not the order the database runs them. A reference for the logical execution order (FROM → WHERE → GROUP BY → HAVING → SELECT → ORDER BY → LIMIT), why aliases fail in WHERE, when to use WHERE vs HAVING, and the MySQL/PostgreSQL differences that bite.

Use Case
2026-08-04

CREATE TABLE Reference: MySQL vs PostgreSQL vs SQLite Types & Constraints

A cross-database CREATE TABLE (DDL) reference with cheat sheets for data types, auto-increment keys (AUTO_INCREMENT / IDENTITY / rowid), foreign key ON DELETE behavior, and the CHECK constraint that MySQL silently ignores.

Use Case
2026-07-14

Mermaid ER Diagram Syntax Reference: Relationship Symbols & Real Examples

Complete reference for Mermaid erDiagram syntax: crow's foot cardinality cheat sheet, one-to-many vs many-to-many, attributes with PK/FK, and a full e-commerce example.

Recent Articles

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curl Options Cheat Sheet: What -X, -H and -d Actually Do

A reference for the curl options you meet in real API work: why -d already implies POST, how -d differs from --data-raw, the @ prefix that silently reads a file, single vs double quotes, and why -k and -L deserve more caution than they usually get.

Introduction
2026-08-06

Converting Between JSON Schema and Zod: How required Maps to .optional()

Inside a two-way converter that turns JSON Schema into a Zod schema and Zod code back into JSON Schema. Covers the inverted defaults between required and .optional(), the constraint mapping table, and how the Zod side is parsed without executing any code.

Use Case
2026-08-06

SQL Clause Order Reference: Why WHERE Can't See Your SELECT Alias

The order you write SQL clauses is not the order the database runs them. A reference for the logical execution order (FROM → WHERE → GROUP BY → HAVING → SELECT → ORDER BY → LIMIT), why aliases fail in WHERE, when to use WHERE vs HAVING, and the MySQL/PostgreSQL differences that bite.

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2026-08-06

Unified Diff Format Reference: Reading @@ Hunks in git diff Output

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2026-08-06

UTC to JST Reference: The 9-Hour Offset, Cheat Sheet & Timezone Pitfalls

Convert between UTC and JST (Japan Standard Time) with a cheat sheet. Covers what Z and +09:00 mean in ISO 8601, when JavaScript date parsing silently shifts by 9 hours, MySQL/PostgreSQL timezone behavior, and why GitHub Actions cron always runs in UTC.

Use Case
2026-08-04

CREATE TABLE Reference: MySQL vs PostgreSQL vs SQLite Types & Constraints

A cross-database CREATE TABLE (DDL) reference with cheat sheets for data types, auto-increment keys (AUTO_INCREMENT / IDENTITY / rowid), foreign key ON DELETE behavior, and the CHECK constraint that MySQL silently ignores.

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