SQL Relationship & Join Analyzer
Joins silently multiply rows when keys aren't unique. Paste two sample tables, choose the keys, and this analyzer tells you the relationship type (1:1, 1:N, N:M), predicts row counts for every join type, and warns about explosions before they hit production.
Sample data is analyzed locally — nothing is uploaded.
Tool interface
Analysis
Expected row counts
Introduction
Most join disasters come from one question nobody asked: is the key unique? This analyzer answers it with your own sample data, classifies the relationship, and predicts exactly how many rows each join type will return.
How to use
- Paste sample CSV for both tables (headers included).
- Enter the key column names.
- Click Analyze relationship and read the row-count table.
Limitations
- Predictions are based on the sample you paste — use representative data.
- Composite keys are not supported in Version 1.0.
FAQ
Is my data uploaded anywhere?
No. Analysis runs locally in your browser.