How to Generate SQL Entity-Relationship (ER) Diagrams from DDL Without a Database

Relational database architectures evolve rapidly during active development. Whether onboarding new team members, conducting architectural design reviews, or documenting schema migrations, having a clear visual Entity-Relationship (ER) diagram is invaluable.

However, traditional database visualization tools require connecting directly to live databases via connection strings, granting read permissions, or installing heavy desktop software. When working on private enterprise databases or sensitive client systems, transmitting connection credentials or uploading proprietary database schemas to cloud SaaS visualizers introduces severe compliance and security risks.

The ideal solution is a client-side visualizer that parses plain text SQL DDL migration scripts directly inside your browser without needing live database access.

OpenTools features a client-side SQL lexer and DDL parser written in pure TypeScript. When you paste your SQL migration script:

1. Tokenization & Grammar Parsing: The parser scans for CREATE TABLE [table_name] blocks and extracts column names, data types (VARCHAR, INT, UUID, TIMESTAMP, etc.), and constraint modifiers (PRIMARY KEY, NOT NULL, UNIQUE, DEFAULT).
2. Foreign Key & Relationship Mapping: It detects both inline foreign key constraints and standalone CONSTRAINT ... FOREIGN KEY (col) REFERENCES foreign_table(col) clauses to establish relationship edges between tables.
3. Grid Coordinate Calculation: A deterministic layout algorithm calculates optimal positions for table cards to minimize intersecting relationship curves.
4. Responsive Vector Rendering: Generates clean, responsive SVG diagrams with table header badges, primary/foreign key icons, and cubic bezier connection paths linking referenced columns.

Paste your standard ANSI SQL schema directly into the SQL to ER Diagram Generator:

```sql CREATE TABLE users ( id UUID PRIMARY KEY, name VARCHAR(255) NOT NULL, email VARCHAR(255) UNIQUE NOT NULL, created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP );

CREATE TABLE orders ( id UUID PRIMARY KEY, user_id UUID NOT NULL REFERENCES users(id), total_amount DECIMAL(10, 2) NOT NULL, status VARCHAR(50) NOT NULL, order_date TIMESTAMP DEFAULT CURRENT_TIMESTAMP );

CREATE TABLE order_items ( id UUID PRIMARY KEY, order_id UUID NOT NULL REFERENCES orders(id), product_name VARCHAR(255) NOT NULL, quantity INT NOT NULL, unit_price DECIMAL(10, 2) NOT NULL ); ```

The visualizer instantly renders a multi-table vector diagram with table headers, primary key identifiers (PK), foreign key links (FK), and smooth relationship lines illustrating the 1-to-many relationship from users $\rightarrow$ orders $\rightarrow$ order_items.

The ER Diagram generator supports: - Zinc Dark & Clean Light Themes: Seamlessly integrate exported diagrams into dark-mode developer documentation (Docusaurus, VitePress) or light-mode corporate technical reports. - High-Resolution SVG & PNG Export: Download lossless vector SVGs for crisp scaling in pitch decks and engineering documentation. - Copy Raw SVG Code: One-click copy of the raw SVG markup for embedding directly into HTML or Markdown documents.