SQL: trustworthy customer reports

SQL · Intermediate

SQL: trustworthy customer reports

Handle missing relationships, NULL values and customer reports without counting mistakes.

Prerequisite: SQL for everyday data · 60 minutes of guided study

2 published lessons, from first principles to a small project.

Open interactive course →

Bridge · From syntax to engineering

Find missing relationships safely with NOT EXISTS
Ask whether a related row exists instead of multiplying rows with a join.
25 min →
Project · Report on customers with no orders
A useful report must define what zero activity means.
35 min →