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Lesson 7 — DISTINCT
DISTINCT: remove duplicate rows
SELECT DISTINCT returns each different value only once. With several columns, a row counts as a duplicate only if all listed columns match. COUNT(DISTINCT column) counts how many different values there are.
SELECT DISTINCT genre FROM movies
SELECT COUNT(DISTINCT genre) FROM movies
Why it matters: "which countries do our customers come from?" is a DISTINCT question — and it is far cheaper than fetching every row.
Want it another way?
Task
Make both queries use DISTINCT. Expected: 3 cities (sorted), and the count 3.
Run your code — when the output matches the task, you will see a green check. Then mark the lesson complete.
Test your knowledge
Test your knowledgeA quick 3-question quiz on this lesson — instant feedback.