上道题用的 union all,这里也试着用了下
计算25岁以上和以下的用户数量
https://www.nowcoder.com/practice/30f9f470390a4a8a8dd3b8e1f8c7a9fa
SELECT
'25岁以下' AS age_cut,
SUM(CASE WHEN IFNULL(age, 1) < 25 THEN 1 ELSE 0 END) AS number
FROM
user_profile
UNION ALL
SELECT
'25岁及以上' AS age_cut,
SUM(CASE WHEN age >= 25 THEN 1 ELSE 0 END) AS number
FROM
user_profile;
