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SQL to ER Diagram

Paste SQL DDL and visualize tables, columns, primary keys, and foreign key relationships as an ER diagram.

Examples

SQL DDL input

ER diagramReady

Your ER diagram will appear here.

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Move this preview into a nearby workflow for conversion, debugging, or export.

DBML to ER Diagram

Convert DBML table definitions and refs into a Mermaid ER diagram.

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Prisma Schema Diagram

Convert Prisma model blocks into an ER-style schema diagram.

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JSON Schema Visualizer

Inspect JSON Schema properties, types, required fields, and composition groups.

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How to use

1Paste CREATE TABLE statements that include primary keys and foreign key relationships.
2Review the generated ER diagram for missing tables, unexpected one-to-many relationships, and join tables.
3Check *_id columns that imply relationships but do not have explicit constraints.
4Trim unrelated tables when documenting one bounded context or feature area.
5Export the diagram after the relationships match the schema you intend to publish.

Common use cases

Database documentationSchema reviewData model onboardingMigration reviewForeign key auditER diagram for README docs

Related tools

DBML to ER Diagram

Convert DBML table definitions and refs into a Mermaid ER diagram.

Prisma Schema Diagram

Convert Prisma model blocks into an ER-style schema diagram.

JSON Schema Visualizer

Inspect JSON Schema properties, types, required fields, and composition groups.

FAQ

Does this use AI?

No. This tool runs parsing and visualization locally in the browser.

What SQL should I paste for the clearest ER diagram?

Use focused CREATE TABLE statements with primary keys, foreign keys, and join tables. Avoid dumping unrelated schemas into one diagram.

Can this find missing foreign key constraints?

It can make suspicious relationship patterns visible, such as *_id columns without constraints, but you should confirm the database rules in migrations or schema docs.

SQL to ER Diagram converts CREATE TABLE DDL into Mermaid ER diagrams for database documentation, schema review, and onboarding.

Use it to inspect tables, columns, primary keys, foreign keys, join tables, and relationship direction before a migration or documentation update ships.

DiagramPreview keeps the SQL source editable so you can revise a focused schema snippet and regenerate the visualization quickly.

Demo: convert CREATE TABLE statements into an ER diagram

SQL schema review becomes faster when tables, primary keys, and foreign keys are visible. The preview helps teams discuss relationships before migrations reach production.

Include CREATE TABLE statements for all referenced tables.
Keep foreign key constraints in the sample when possible.
Use the ER output to review relationships, not query performance.

CREATE TABLE users (id INT PRIMARY KEY, email TEXT);
CREATE TABLE orders (id INT PRIMARY KEY, user_id INT REFERENCES users(id), total DECIMAL);

Review checklist: catch schema relationship mistakes

An ER preview can expose missing foreign keys, many-to-many join tables, and columns that imply a relationship but are not constrained.

Look for *_id columns without a matching relationship.
Check whether join tables need composite uniqueness.
Confirm nullable foreign keys represent a real optional relationship.

order_items(order_id, product_id)
UNIQUE(order_id, product_id)

Migration review: diagram only the tables that changed

For database migrations, a smaller ER diagram is usually more useful than a full schema dump. Focus on the tables touched by the migration and their nearest dependencies.

Include referenced parent tables so foreign keys have context.
Call out new nullable foreign keys because they often change application behavior.
Use the diagram in PR review alongside the migration diff.

CREATE TABLE subscriptions (
  id INT PRIMARY KEY,
  account_id INT NOT NULL REFERENCES accounts(id),
  plan_id INT REFERENCES plans(id)
);

Review checklist for SQL to ER Diagram

Use SQL to ER Diagram when you need to inspect source content visually before it becomes documentation, a pull request note, an incident write-up, or a handoff artifact. Convert CREATE TABLE SQL into a Mermaid ER diagram.

Before exporting, check that labels are readable, relationships match the source, generated examples do not contain private data, and the preview still makes sense after you edit the input.

Limits and troubleshooting

If the preview fails, reduce the input to the smallest complete example, confirm the format syntax, and then add sections back one at a time. Many rendering failures come from partial files, indentation mistakes, missing diagram headers, or copied snippets that depend on hidden context.

Treat the preview as a review surface rather than a source of truth. Generated diagrams, converted files, dashboards, and rule examples should be checked before they are used in production documentation or operations.

Example inputs to test

Commerce: CREATE TABLE customers ( id INT PRIMARY KEY, email VARCHAR(255) NOT NULL UNIQUE, name VARCHAR(120) ); CREATE TABLE orders ( id INT PRIMARY KEY, customer_id INT NOT NULL REFERENCES ...
Blog: CREATE TABLE authors ( id INTEGER PRIMARY KEY, display_name TEXT NOT NULL ); CREATE TABLE posts ( id INTEGER PRIMARY KEY, author_id INTEGER REFERENCES authors(id), slug TEXT NOT NU...
Billing: CREATE TABLE accounts ( id BIGINT PRIMARY KEY, plan VARCHAR(40) NOT NULL ); CREATE TABLE invoices ( id BIGINT PRIMARY KEY, account_id BIGINT NOT NULL, amount_cents INT NOT NULL, FO...

Tool maturity

Stable renderer

Stable tool

This tool has a dedicated renderer or preview surface, useful exports, and a repeatable browser-first workflow.

The maturity label is not a quality score. It tells visitors whether the tool is best for stable export, deeper debugging, quick parsing, or AI-assisted generation.