Schema Lens
Instant ERD diagrams from your SQL, Prisma, Drizzle, and Knex migrations. No database connection required.
Open your migration file → click ≋ Schema Lens Icon → live diagram updates as you edit. Vibe-coded in public, AGPLv3 licensed.
Install from VS Code Marketplace | GitHub
The Problem
You get handed schema.sql, schema.prisma, or 2024_init.ts.
- No ERD exists
- No database to connect to
- Your brain has to reconstruct relationships manually
- Code reviews take 3× longer
- Onboarding new devs = pain
The Fix
- Open any migration file (
.sql, .prisma, Drizzle schema.ts, Knex migrations)
- Click ≋ ERD in the editor title bar
- Live, interactive ERD appears in a side panel
- Edit the file → diagram updates instantly on save
No database. No cloud. Just your files.
See It Work
| Format |
Example |
| Raw SQL |
CREATE TABLE users (id SERIAL PRIMARY KEY, email TEXT UNIQUE) |
| Prisma |
model User { id Int @id @default(autoincrement()) email String @unique } |
| Drizzle |
pgTable('users', { id: serial('id').primaryKey(), email: text('email').notNull().unique() }) |
| Knex |
table.increments('id'); table.string('email').unique() |
Install
Option 1 — Marketplace UI
- Open VS Code Extensions (
Ctrl+Shift+X)
- Search Schema Lens
- Click Install
Option 2 — CLI
code --install-extension SangeethPromod.schema-lens
Option 3 — Direct link
marketplace.visualstudio.com → Schema Lens
Open any .sql / .prisma / Drizzle / Knex file → the ≋ ERD button appears automatically in the title bar.
Works offline after install.
Usage
Open an ERD
- Open a supported schema file
- Click ≋ Schema Lens in the editor title bar, or run Schema Lens: Open ERD from the Command Palette (
Ctrl+Shift+P)
- ERD opens in a side panel — zoom with scroll wheel, pan by click-dragging
Diff Mode (Beta, may run into edge case issues)
Compare two schema files visually:
- Open a schema file
- Run Schema Lens: Compare With… from the Command Palette
- Select a second file
- Diff ERD opens with:
- 🟢 Added tables and columns
- 🔴 Removed tables and columns
- 🟡 Modified tables
| Format |
File Pattern |
How It's Parsed |
| Raw SQL |
*.sql |
node-sql-parser — CREATE TABLE, ALTER TABLE, FOREIGN KEY |
| Prisma |
schema.prisma |
Line-based parser — model blocks, fields, @relation |
| Drizzle |
*.ts with pgTable / mysqlTable / sqliteTable |
TypeScript AST walk |
| Knex.js |
*.ts with createTable |
TypeScript AST walk |
Auto-detection for .ts files: Drizzle is preferred if both patterns are present.
Known Limitations
- SQL dialects — targets PostgreSQL and MySQL. Vendor-specific syntax (e.g., SQL Server
IDENTITY) may not parse cleanly.
- Prisma enums —
enum blocks are ignored; they won't appear in the ERD.
- Composite foreign keys — fully supported in SQL; ORM parsers handle common patterns, complex composites may not render perfectly.
- Views, procedures, functions — not parsed; not shown.
- Large schemas — 50+ tables can feel heavy. Zoom and pan to navigate.
- Block comments —
/* ... */ inside CREATE TABLE definitions can confuse the parser in some edge cases.
Always verify generated ERDs against your actual schema.
Pre-1.0: Vibe-Coded with Guardrails
Built fast, shipped fast, learning in public.
- Tests + CI on every PR
- AGPLv3: use it freely, improve it, share improvements back
- Rough edges expected — file issues, send PRs
This is not production-hardened tooling. It is a dev utility that solves a real problem. Use accordingly.
Contribute
git clone https://github.com/sangeethPromod/schema-lens
cd schema-lens
npm install
npm test
- Fork → branch → PR to
main
npm test must pass before pushing- Good first issues: labeled here
Wanted contributions:
- Parser bug fixes for your ORM / SQL dialect
- MongoDB / Mongoose support
- ERD diff view between migration versions
- Better dark mode theming
- Performance improvements for large schemas
Schema Lens is licensed under the GNU Affero General Public License v3.0.
Copyright (C) 2026 Sangeeth Promod
Built in Kerala. Vibe-coded for developers everywhere.
