SQL for Product Managers
How a Database Is Actually Organized
A database is a set of spreadsheets that know how to talk to each other. That's the whole concept.
Forget anything intimidating you've heard about databases. At the core, almost every database you'll touch as a PM is organized into tables, and a table is a spreadsheet: rows going down, columns going across.
A table is one spreadsheet - users, orders, events, subscriptions.
A row is one record - one specific user, one specific order.
A column is one attribute of every record - email, signup_date, plan_type.
Here's a tiny users table:
id | signup_date | plan | |
|---|---|---|---|
101 | anna@acme.com | 2026-01-04 | pro |
102 | ben@zenith.com | 2026-01-06 | free |
103 | carla@nova.io | 2026-01-09 | pro |
And a tiny orders table:
id | user_id | amount | order_date |
|---|---|---|---|
9001 | 101 | 49.00 | 2026-01-10 |
9002 | 101 | 49.00 | 2026-02-10 |
9003 | 103 | 149.00 | 2026-01-12 |
Notice orders.user_id contains values that match users.id. That's not a coincidence, it's the entire mechanism that lets a database connect two tables together. This is called a key.
Term | Plain English | Example above |
|---|---|---|
Primary key | The column that uniquely identifies each row in its own table | users.id |
Foreign key | A column in one table that refers to a primary key in another table | orders.user_id refers to users.id |
Relationship | The logical connection this creates | "Each order belongs to exactly one user" |
Every product database you'll ever query is some version of this pattern, scaled up: dozens or hundreds of tables, connected through keys, each table holding one kind of thing. Once this clicks, an unfamiliar schema stops being intimidating. It's just spreadsheets you haven't opened yet, connected by IDs.
YOUR MOVE THIS WEEK
Ask a data engineer or analyst to show you a diagram of your product's core tables - users, orders, events, whatever your product has. Just look at it. Identify three tables and, for each, what one row represents. You don't need to understand every column yet, just the shape.