mysql - 哪个sql语句应该是正确的？

Question

我有一个 sql 问题。

web_requests: date, user_id, browser [chrome, firefox, ie], request_count

api_reques‍‍‍‍‍‍‍‌‍‌‍‌‌‌‌‌‍‌‌ts: date, user_id, devide_type [iphone, ipad, android-phone], request_count

目标:获取自年初以来每天在同一天在 iPhone 和 Web 上至少访问过一个页面的用户数

我在这里尝试了两种不同的sql，我想知道哪种更好？

1.

select w.date, sum(w.user_id) + count(a.user_id) as per-day-count
from 
(select * from web_requests where date >= '2017-01-01') as w

inner join

(select * from api_requets where device_type = 'iphone' and date >= '2017-01-01') as a
on w.date = a.date and w.user_id = a.user_id

2.

select date, count(distinct use‍‍‍‍‍‍‍‌‍‌‍‌‌‌‌‌‍‌‌r_id) as users
    from
    (
            select date, user_id
            from api_request
            where device_type = 'iphone' and date >= '2017-01-01' and request_count > 0
            UNION
            select date, user_id
            from web_request
            where date >= '2017-01-01' and request_count > 0
    ) a
    group by date

Answer 1

您可以像这样构建此查询。首先是获取 union 中的 count() 并获取结果表的 sum。

select date, sum(ct) from (
    select count(1) as ct, user_id, date, 'web' as src from web_requests 
        where date >= '2017-01-01'
        group by date, user_id
    union
    select count(1) as ct, user_id, date, 'api' as src from api_requets 
        where device_type = 'iphone' and date >= '2017-01-01'
        group by date, user_id
) t1
group by t1.date