Welcome, I'm John at Maven Analytics. I have over 15 years of business intelligence experience, having worked with companies ranging from Fortune 500 to early-stage startups. I’ve performed leadership roles across analytics, marketing, SaaS and product teams.

If you've done some SQL before, you can SELECT, WHERE, and GROUP BY with reasonable confidence. But here's the thing most tutorials don't tell you upfront: in a real analyst role, the data you need is almost never in one table.

Customers are in a customers table. Products are in a products table. Orders reference both by ID. To answer a question like "which customer segment is driving revenue?", you need to connect all three. That connection is a JOIN. And if you can't write one cleanly, there's a hard ceiling on the business questions you can answer.

Over the next 5 days, you'll investigate a real business problem at Apex Retail: understanding which customers drive the most value, and whether certain segments are worth investing in for retention. Every answer requires multiple tables. Every query builds on the last.

Today: your first JOIN. By the end of this email, you'll have answered a question your single-table queries simply couldn't.

The scenario

Sarah (Head of Commerce) has a brief for you:

• "I want to understand our customers, not just what sold, but who's buying, and whether our VIP segment is actually worth the investment we make in them."

The orders table has revenue. The customers table has segment information. Neither alone can answer the question. A JOIN connects them.