题解 | 计算25岁以上和以下的用户数量

# select
#     '25岁以下', count(id)
#     # count(id) as "25岁以下"   # 这个写法输出不了
# from
#     user_profile
# where
#     age<25 or age is null or age=''

# union all

# select
#     '25岁及以上', count(id)
#     # count(id) as "25岁以下"   # 这个写法输出不了
# from
#     user_profile
# where
#     age>=25 

SELECT 
    CASE
        WHEN age >= 25 THEN '25岁及以上'
        ELSE '25岁以下'
    END as age_cut,
    COUNT(id) as number
FROM user_profile
# GROUP BY 
#     CASE
#        WHEN age >= 25 THEN '25岁及以上'
#        ELSE '25岁以下'
#     END;
group by
    age_cut;

新方法不是很明白