Turn SQL tables into an ER diagram you can review

Free ER Diagram is a browser-based database documentation tool. Paste CREATE TABLE statements to visualize tables, columns, primary keys, foreign keys, and relationships as Mermaid or PlantUML output. No account is required, and SQL parsing happens in the browser.

The generated diagram is a review aid. Compare it with the source DDL before relying on it for migrations or production documentation, especially when a schema uses engine-specific constraints or relationships enforced only by application code.

A practical review workflow

• Parse the DDL and verify that every expected table, key, and column appears.
• Check nullable foreign keys, unique constraints, join tables, and self-referencing relationships.
• Add relationships that are enforced by application logic but are absent from the SQL.
• Group tables by business domain, then export or share the reviewed diagram.

Learn with tested examples

Start with the inventory schema or multi-tenant SaaS schema, then read the foreign-key relationship guide. The parser coverage and limitations page documents what the current implementation recognizes and what must be checked manually.