Generate ER Diagram from SELECT Queries (JOIN Analysis Tool)

pomuchan02 — Mon, 23 Mar 2026 05:36:30 +0000

No installation required. Runs entirely in your browser.

Introduction
When working with existing systems, have you ever struggled with complex SQL like this?

Too many JOINs to understand the structure
Hard to visualize table relationships
No ER diagram available I had the same problem, so I built a tool that generates ER diagrams directly from SELECT queries.

👉 Try it here: SQL2ER

【Free】SQL to ER Diagram Generator | SQL2ER

trancelens.com

↓

What This Tool Does
You can paste a SELECT query, and it will automatically generate an ER diagram based on JOIN relationships.

Example

SELECT
  u.name,
  o.id,
  p.name
FROM users u
JOIN orders o ON u.id = o.user_id
JOIN order_items oi ON o.id = oi.order_id
JOIN products p ON oi.product_id = p.id;

👇

The tool analyzes JOIN conditions like:

u.id = o.user_id

and converts them into relationships between tables.

Why This Is Useful
Most existing tools (like DDL-based ER generators) require CREATE TABLE statements.

However, in real-world scenarios:

You often only have SELECT queries
You’re analyzing legacy systems
You want to quickly understand relationships 👉 This tool works without any DDL

Key Features

No installation required (runs in browser)
Works with plain SELECT queries
Supports multiple JOINs
Handles table aliases

How It Works
The logic is simple:

SELECT query
↓
Parse JOIN and ON clauses
↓
Extract relationships
↓
Generate ER diagram
Specifically, it detects patterns like:

table1.column = table2.column

and builds connections from them.

Use Cases

Understanding legacy systems
SQL code reviews
Learning database relationships
Debugging complex queries

Try It Yourself
👉 http://trancelens.com/sql2er/en/index.html

Paste your SQL and see the structure instantly.

Final Thoughts
There are many tools that generate ER diagrams from CREATE statements.

But generating them from SELECT queries turned out to be surprisingly useful in practice.

If you deal with SQL regularly, this might save you a lot of time.

Feedback
I’d love to hear your fee

DEV Community: pomuchan02

Generate ER Diagram from SELECT Queries (JOIN Analysis Tool)

【Free】SQL to ER Diagram Generator | SQL2ER