Question

我编写了以下查询，该查询计算每个客户的订阅“类型”，并显示订阅名称以及与之关联的客户数量。它有效。

例如：

订阅A = 200个客户订阅B = 57

select 
   subscription_name, count(subscription_name) as Num_of_Customers 
from 
  subscription
    join customer on subscription.subscription_number=customer.subscription_number
group by subscription_name;

我无法弄清楚如何显示“ONLY”具有最多客户数量的订阅名称。

我非常感谢你的建议。感谢。

Answer 1

您可以按客户数量排序结果，并将结果限制在第一行：

您没有提到您正在使用的DBMS，并且在不同系统中这样做的方式不同：

MYSQL - 在LIMIT 1后使用ORDER BY：

select subscription_name, count(subscription_name) as Num_of_Customers
from subscription
join customer on subscription.subscription_number = customer.subscription_number
group by subscription_name
order by count(subscription_name) desc
limit 1;

SQL-SERVER - 使用SELECT TOP 1

select top 1 subscription_name, count(subscription_name) as Num_of_Customers
from subscription
join customer on subscription.subscription_number = customer.subscription_number
group by subscription_name
order by count(subscription_name) desc;

Oracle - 使用ROWNUM

select * from  
( select subscription_name, count(subscription_name) as Num_of_Customers
    from subscription
    join customer on subscription.subscription_number = customer.subscription_number
    group by subscription_name
    order by count(subscription_name) desc 
) a
where ROWNUM = 1;

如果您正在使用其他DBMS，您也可以看到如何做到这一点的想法。

查询结果的编号最高

1 个答案: