使用 JOIN 和 COUNT 求总数 SQL

Question

我是 SQL 的超级新手，一直在研究这个查询，但似乎无法让它发挥作用。我需要总结类别（每个国家有多少客户以及每个员工有多少客户）。这是我试图获得每个国家/地区的总客户数的方法：

COUNT(*) TotalCount,
country.id, country.country
FROM client
INNER JOIN country
ON client.country_id = country.id
GROUP BY country.id, country.country

这些是我的表格：

CREATE TABLE employee(
    id INT AUTO_INCREMENT PRIMARY KEY,
    employee VARCHAR(40)
);

CREATE TABLE country (
    id INT AUTO_INCREMENT PRIMARY KEY,
    country VARCHAR(40)
);

CREATE TABLE client(
    id INT AUTO_INCREMENT NOT NULL PRIMARY KEY,
    name VARCHAR(40),
    email VARCHAR(40),
    sold BOOLEAN,
    date VARCHAR(40),
    email_type_id INT,
    employee_id INT,
    country_id INT,

    FOREIGN KEY(email_type_id) REFERENCES email_type(id),
    FOREIGN KEY(employee_id) REFERENCES employee(id),
    FOREIGN KEY(country_id) REFERENCES country(id)
);

非常感谢！

Answer 1

每个国家有多少客户

select country , count(*) from country  inner join client on country.id=client.country_id 
group by country

每个员工有多少个客户

Select employee , count(*) from employee inner join client on client.employee_id =employee.id group by employee

Answer 2

国家/地区计数：

SELECT country , count(*) as countryCount from country INNER JOIN client on country.id=client.country_id GROUP BY country;

员工人数：

SELECT employee , count(*) as empCount from employee INNER JOIN client on client.employee_id =employee.id GROUP BY employee;

您也可以点击这个查询:::

SELECT country , count(country) as countryCount from country INNER JOIN client on client.country_id=country.id GROUP BY country;

SELECT employee , count(employee) as empCount from employee INNER JOIN client on employee.i=client.employee_id GROUP BY employee;

在count()中，我已经传递了列名。

使用 JOIN 和 COUNT 求总数 SQL

Using JOIN and COUNT to find totals SQL

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