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SELECT
CASE
WHEN u.age BETWEEN 1 AND 19 THEN 'Juniors'
WHEN u.age BETWEEN 20 AND 50 THEN 'Seniors'
WHEN u.age > 50 THEN 'Masters'
ELSE 'Undefined'
END AS age_group,
COUNT(r.rating_id) AS rating_count
FROM
users u
JOIN
ratings r ON u.user_id = r.user_id
GROUP BY
age_group;
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SELECT Manufacturer, COUNT(*) AS ModelsCount
FROM Products
WHERE Price > 30000
GROUP BY Manufacturer
ORDER BY ModelsCount DESC
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SELECT
c1, c2, , cn, aggregate_function(ci)
FROM
table
WHERE
where_conditions
GROUP BY c1 , c2, ,cn;