用于查找每个给定位置的最多供应商数量的 SQL 查询

Question

您能帮我找到正确的 MySQL 查询，以获取每个给定位置的最多供应商数量，并按名称和商店名称列出所有供应商吗：

1 - 查询必须找出哪个位置的供应商数量最多，然后按名称和他们工作的商店的名称列出它们。

我有以下表格：

CITIES 
(
 ID "unique",
 NAME
)


SHOPS
(
 ID "unique",
 NAME,
 CITY_ID ( foreign key of CITIES TABLE ID)
)

VENDORS
(
 ID "unique",
 NAME,
 SHOP_ID ( foreign key of SHOPS TABLE ID)
)

虚拟数据示例

CITIES : NY, SF

SHOPS: Boom - NY, Flash - NY, Sofast - SF

Vendors:

Mark : Boom,
John : Boom,
Carlos : Sofast,
Alex : Sofast,
David : Flash,
James: Flash

纽约的供应商数量最多，因此应该列出

Mark : Boom, John : Boom, David : Flash, James: Flash

Answer 1

检查这是否有效 -

Select vendors.name, shops.name 
from 
cities inner join shops on cities.id= shops.city_id
inner join vendors on shops.id = vendors.shop_id
where cities.id = (select id from (select cities.id, count(1) from 
cities inner join shops on cities.id= shops.city_id 
inner join vendors on shops.id = vendors.shop_id 
group by cities.id order by 2 desc) limit 1)

Answer 2

如果您运行的是 MySQL 8.0，您可以使用窗口函数来解决这个问题：

select *
from (
    select x.*, rank() over(order by cnt) rn
    from (
        select v.*, count(*) over(partition by c.id) cnt
        from cities c
        inner join shops   s on s.city_id = c.id
        inner join vendors v on v.shop_id = s.id
    ) t
) t
where rn = 1

最内部的查询连接三个表，并计算每个城市有多少供应商。下一级按降序排列记录。最后，最后一级过滤排名靠前的行。