Question 1

How does the SQL DDL to ER Diagram Generator work?

Accepted Answer

Paste your CREATE TABLE / ALTER TABLE DDL (MySQL, PostgreSQL, SQLite, SQL Server, or ANSI-compatible) and the tool parses it into an in-memory schema model — tables, columns with types/nullability, primary keys, unique constraints, indexes, and foreign keys (inline REFERENCES, table-level FOREIGN KEY, or ALTER TABLE ADD FOREIGN KEY). From that model it emits a Mermaid erDiagram, an ASCII crow's-foot diagram, and DBML, plus a topologically-sorted creation order. Everything runs in your browser; no DDL is uploaded.

Question 2

Which SQL features and edge cases are supported?

Accepted Answer

Composite primary keys, composite foreign keys, self-referencing FKs (categories.parent_id → categories.id), circular FK chains (topological sort falls back gracefully), inline and table-level FK declarations, ALTER TABLE ADD FOREIGN KEY, named and inline constraints, multi-word types (CHARACTER VARYING, DOUBLE PRECISION, TIMESTAMP WITHOUT TIME ZONE), and quoted identifiers (`backtick`, "double-quote", [bracket]). CHECK constraints are detected and flagged but not interpreted. Naming-based relationship inference (e.g. user_id → users.id) can be enabled to draw FK edges when explicit REFERENCES are missing.

Question 3

What output formats can I export?

Accepted Answer

Mermaid erDiagram code (paste into any Mermaid renderer, GitHub, Notion, or the live editor), a plain-text ASCII crow's-foot diagram, DBML (for dbdiagram.io), and a JSON schema model that round-trips with our companion ER Diagram Designer (#268). You can copy or download any of these, and a shareable URL encodes the entire schema in the fragment so you can send the diagram to a colleague without uploading anything.

Question 4

Does this work offline and without an account?

Accepted Answer

Yes. Parsing, layout, and all export formats are 100% client-side. There is no signup, no API key, and no upload — your DDL never leaves the browser. History (last 20 parses) is stored in localStorage on your device only. The tool is installable as a PWA.

Question 5

What extras does this generator offer versus dbdiagram.io / drawDB / DrawSQL?

Accepted Answer

(1) Multi-dialect DDL parsing (MySQL, PostgreSQL, SQLite, SQL Server, ANSI). (2) Mermaid erDiagram + ASCII crow's-foot + DBML exports from one parse. (3) Composite PK / composite FK / self-ref FK / circular FK support. (4) Naming-based relationship inference (user_id → users.id) when explicit FKs are absent. (5) Auto-layout with table coordinates. (6) Topological sort with cycle detection. (7) Reserved-word detection per dialect. (8) Inline validation warnings (orphan FK targets, missing PK, etc.). (9) JSON schema model export that round-trips with the ER Diagram Designer. (10) Shareable URL with base64-encoded schema. (11) Three DDL presets (blog, e-commerce, m2m). (12) localStorage history (max 20). (13) Copy / download every format. (14) 100% offline, no signup.

SQL DDL to ER Diagram Generator

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