GROUP BY

What it is

GROUP BY collects rows for aggregate calculations.

When to use it

Summarize by customer, status, or currency.

Syntax

SELECT user_id, SUM(total_cents) FROM orders GROUP BY user_id;

Example

SELECT user_id, COUNT(*) AS order_count, SUM(total_cents) AS total_cents
FROM orders WHERE status = 'paid'
GROUP BY user_id HAVING COUNT(*) >= 2;

Common mistakes

Group all nonaggregated selected columns; WHERE filters rows, HAVING filters groups.

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