Keys

Keys

Keys is a core part of SQL. In this case file you'll learn what it is, why it matters, and how to use it in real code.

Understanding keys well means you can read other people's SQL code with confidence, and avoid the most common beginner mistakes in this area.

Key points:

• What keys means in the context of SQL
• A minimal example you can run or read in the playground on the right
• A common mistake to avoid when working with keys

-- SQL: Keys
SELECT *
FROM agents
WHERE clearance_level > 0;

Tip: Try changing a value in the code on the right and re-running it — small experiments are the fastest way to build real intuition for keys.