如何基于另一个表中值的数量从表中获取记录

Question

所以我有表A（城市）

身份证，城市，国家

和表B（行程）

id，旅行，城市，活跃

我想选择所有使用MySQL的城市，但要按活跃度为1时它们在表B中显示的次数进行排序。

提前致谢

Answer 1

您可以尝试两个查询并比较效果

select a.city, count(*) as cnt
from cities as a
left join
trips as b
on (a.id = b.city and b.active=1)
group by a.city
order by 2 desc

要么

select
    a.city,
    (select count(*) from trips as b where a.id = b.city and b.active=1) as cnt
from cities as a
order by 2 desc

Answer 2

然后将联接B保留在A并在联接子句中包含active = 1条件，并按城市分组。

select a.city, count(b.city) as cnt
from a
left join b on a.id=b.city and b.active=1
group by a.id, a.city
order by count(b.city) desc