SQL THAT WORKS — AT WORK

SQL That Works — At Work

Most SQL courses teach you to pass a test.
Real jobs demand SQL that ships clean data — for dashboards, pipelines, and AI models.

GroupBySQL teaches you the production patterns that actually matter.

What you’ll master here

• Conditional aggregation (pivot active vs canceled in one pass)
• NOT EXISTS (find missing data 100× faster)
• Window functions & date spines for accurate cohorts
• Clean, structured outputs ready for Looker, dbt, or LLMs

Open the Playground See all guides

How it works

Real tickets — challenges copied from actual Slack/email requests
Short guides — 5-minute reads that link directly to the problem
Interactive playground — write, run, and compare solutions instantly

Why this matters in 2025

SQL is still the #1 tool analysts and engineers use every day.
The difference between “I can write SQL” and “I own the insight pipeline” is mastering these exact patterns.

AI Feature Engineering

Learn to structure SQL outputs (JSON) to feed LLMs, classifiers, and clean data pipelines.

Query School

Short, production-grade SQL guides that map directly to the challenges in the Playground.

Browse guides →

Why I built GroupBySQL

Most SQL resources teach you to pass tests. Real jobs demand clear thinking, messy data, and executive outcomes. GroupBySQL trains analysts to think in systems, translate insights, and reliably ship data features — with fewer, better challenges.