Question

我想进行查询，以便我只能抓住至少有50个地方的地点。

我有一张地点表：

Id, City, Country
1, Austin, USA
2, Paris, France

通过Location_id连接到地点的地方信息表

Id, Name, Details, Location_id
1, The Zoo, blah, 2
2, Big Park, blah, 2

我可以这样加入他们：

SELECT places.name，places.id，locations.country，locations.city 从地方 INNER JOIN位置 ON places.location_id = locations.id

我怎样才能获得至少有50个地方的城市的结果，并以最大的数量订购？

谢谢！

Answer 1

使用GROUP BY with a HAVING条款。

SELECT locations.country, locations.city, COUNT(*)
FROM places
     INNER JOIN locations ON places.location_id = locations.id
GROUP BY locations.country, locations.city
HAVING COUNT(*) >= 50

Answer 2

好的我已经看到上述答案几乎存在，但有一些错误，所以只需发布正确的版本：

SELECT locations.country, locations.city, COUNT(*) as count_of_places
FROM places
     INNER JOIN locations ON places.location_id = locations.id
GROUP BY locations.country, locations.city
HAVING COUNT(*) >= 50
ORDER BY count_of_places;

Answer 3

您可以使用having子句将这些行限制为聚合列的值。此外，MySQL允许您使用惰性group by，因此您绝对可以利用此功能：

select
    l.country,
    l.city,
    p.name,
    p.details,
    count(*) as number_of_places
from
    locations l
    inner join places p on
        l.id = p.location_id
group by
    l.id
having
    count(*) >= 50
order by
    number_of_places,
    l.country,
    l.city,
    p.name

Answer 4

有点不了解，但应该有效：

SELECT places.name, places.id, sq.country, sq.city, sq.counter FROM (SELECT Locations.id, country,city, count(*) as counter FROM Locations JOIN Places ON (Locations.Id=Places.Location_id) GROUP BY locations.id HAVING count（*）＆gt; = 50）AS sq JOIN Place ON（sq.id = Places.Location_id） ORDER BY counter DESC` < / p>

P.S。确切的语法可能因数据库而异，我不确定这是mysql - 是否兼容。

有关计数的SQL问题

4 个答案: