Question

我有一个包含两个变量的表，每个变量出现一次，每个变量出现一次：

即

Customer        City
Bob             New York
Bob             Denver
Bob             Denver
Greg            Denver
Greg            Denver
Greg            New York

示例：

SELECT Customer FROM tableName WHERE COUNT( SELECT Customer,City FROM tableName)=1;

我想为每个独特的客户名称获取独特的城市，并计算客户拥有的城市数量。你如何在mysql中做到这一点？

Answer 1

您可以使用distinct来电中修改的count：

SELECT   customer, COUNT(DISTINCT city)
FROM     tablename
GROUP BY customer

Answer 2

我不确定您是希望为每个客户重复一个城市还是不同城市的总数，因此我将同时考虑这两个值：

select Customer, City, count(City) as CityCount, TotalDistinctCities
from CustomerCities
join (select Customer as cust, count(distinct City) as TotalDistinctCities
  from CustomerCities
  group by Customer)
as CityCount on cust=Customer   
group by Customer, City, TotalDistinctCities

基于条件SELECT的COUNT

2 个答案: